Why Does United Change Its Flight Numbers So Often? (Ask Cranky)

Schedule Changes, United

It’s time for another Ask Cranky question, and you United frequent fliers will probably be very interested in this one.

Hey Cranky,

Really curious about something; hoping you can answer it on your blog (or otherwise).

Why does United have flight numbers that seem to change day to day / week to week? Maybe I’m Ask Crankyimagining it, but it seems more haphazard than other airlines’ flight numbering schemes.

See e.g. on United’s timetable PDF, all the 7:44AM flights from FLL to DEN. There are a bunch of different listings — a few of them share flight #s, but most of them don’t, even though they’re the same times/same equipment.

I keep noticing this when I want to see whether today’s flight 123 came in on time yesterday (for fun, mostly), and yesterday’s flight 123 is a completely different segment.



You are not seeing things, Tevi. United does seem to vary its flight numbers a lot, and it’s really strange. I went to United to get some answers on this one.

To start, it’s important to keep in mind that flight numbers are scarce resources. Every system is coded to have four-digit flight numbers and no more. That was fine back in the day, but today with mega-carriers and codeshares, that’s not really enough anymore. The cost involved to move to a five-digit flight number is substantial, and I don’t imagine it’s going to happen anytime soon. Gone are the days where even-numbered flights went one direction and odd-numbered flights went the other, with flight numbers not changing for years. Airlines today need to do what they can to maximize flight number usage.

During mergers, things get even more compressed as airlines end up having to codeshare with each other. During United’s merger with Continental, the numbers were carved up. Most of pre-merger Continental’s long haul flights used numbers between 1 and 199. Pre-merger United used 200-999 (with most Asian flights using the historic 800 series and European flights using the historic 900 series). Pre-merger Continental shorter haul flying fell into the 1000-1764 range (with a few cutouts in the middle). Above that? Express carriers (with each carrier having its own dedicated range) and then codeshare partners beyond that. You can follow it all the way up to United flight 9998, a flight from Brussels to Vienna operated by Brussels Airlines.

That’s a lot to pack into 9,999 flight numbers, and United decided to get creative. So it was back in late 2012 when United introduced a new system that would optimize flight numbers. It would randomly look at the schedule every day and, using some parameters, would spit out a list of flight numbers to be used. What were those parameters?

There were the usual things, like trying to keep prominent flight numbers on regular routes (mostly long haul). But it was more than that. Even though the need for segregating United and Continental operations by flight number range had passed, United opted to continue to do things along those lines for operational reasons. It’s not actually a strict Continental/United breakdown anymore. It’s more about fleet type. For example, there are some 737-900s that were technically delivered to the United side and those operate under the same flight number ranges as the other 737-900s on the Continental side.

The airline apparently liked this internally because it could know a lot about a flight just by looking at the flight number. But this didn’t consider that from a customer perspective, it was really confusing.

For example, let’s stick with Ft Lauderdale to Denver. Today, United has a 320p flight on an A320. That’s flight 780. But tomorrow, it’s a 630p flight on a 737-900. That’s flight 1571. On Saturday, it’s back to a 325p flight on an A320 but the flight number is 764.

But that’s not all. The morning flight leaves at 744a today as flight 1452 on a 737-900. Tomorrow it’s a 737-800 and moves to flight 1758. Sunday, it’s back to a 737-900 but it now leaves at 736a. It’s flight 1736. Monday it’s still a 737-900 but it leaves at 746a and it’s flight 1660. What gives?

Some of the problem lies in shifting daily schedules. These days, airlines optimize their schedules by day, so it’s easy to just re-optimize every day and not really worry about consistency during the week. That’s how United has run things for the past couple years.

Most airlines don’t switch things around so much, and United has apparently decided to change its ways as well. According to a spokesperson, the April schedule change is going to have a new focus on trying to keep flight numbers regular. Now, flipping through Ft Lauderdale to Denver doesn’t show much regularity, but maybe it’ll become more apparent in other markets.

But do passengers even really care? Many don’t think twice about the flight number, but frequent fliers are likely to notice. And even though it’s a small group that might care, it’s apparently enough that United has decided to make a change. Keep an eye on that April schedule.

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48 comments on “Why Does United Change Its Flight Numbers So Often? (Ask Cranky)

  1. I personally don’t even look at flight numbers, so I never noticed that United was doing this. But it’s an interesting article nonetheless.

  2. Interesting, I always figured that it had to do with DOT statistics. Switch up your flight numbers often so that chronically delayed flights look much less chronically delayed.

      1. That may be, but when you look for flights on booking sites, if the number has changed, the websites aren’t sophisticated enough to get the data. Therefore the flights lists as having no history when you go to purchase the ticket.

      2. When the flight number is changed airline/travel agent computers will show it as -N- for a new flight so there is no on time data shown like 3,4,5 etc for 30pct on time, 40pct on time, etc. So even if the actual flight has been operating between the same two cities at the same times for years, it erases the old on time stat which could have been really bad and give it a fresh start. It’s like painting your house, its the same house but a new coat of paint will make it seem better.

    1. I agree with Mike, I had always assumed it was a way to submerge bad departure and arrival data with a new flight number. Is it possible that UA is making more work for itself than honestly necessary and they seem to forget that passengers like a bit of consistency. AA’s #42 always flies from ORD to CDG, with 41 being the return. They are doing a bit of stretching by using the same flight number both directions in a simple turn, but that may have to do with redundancies at US Airways.

      1. For the most part, I believe the article was referencing domestic flying. UA keeps the same flight number for international flights (long haul).

    1. In case when there are 2 flights with the same number in the air at the same time, the pilot adds a letter (e.g., tango) to the end of flight number for unique call sign.

      1. These are called “radio numbers” and serve to avoid any flight number conflicts in common airspace. The radio numbers are typically managed by dispatchers, not pilots.

    2. The FAA monitors published flight numbers and notifies airlines of potentail conflicts to prevent this.

  3. consistency is nice as a business flier, but not needed. If UA can learn a/c type from flight number, that’s pretty cool. Wonder if they will create/keep some of the “special” numbers airlines have had over the years. Some of my favorites:

    b6 777 / 711 – BOS-LAS
    UA 500 – IND-SFO
    CO 1492 IAH-CMH
    NW 1776 DTW-PHL

      1. The Schedulers at JetBlue have gotten fancy with this as well.
        BOS-PHL – 1776
        ABQ – JFK – 66

        those are the ones i remember off the top of my head. There are a few more like that.

    1. I’ve flown on PMUA 1492 BUR-DEN-CMH, one stop same plane connection. Ironically, some of my Denver-based colleagues would board the second segment, and their one-way airfare was more expensive than my roundtrip from BUR.

  4. Maybe it is the cynic in me, but is it possible that tweaking the flight numbers and/or times cooks the numbers United needs to report for on-time performance? (Which are not very good to begin with.) I travel the same route weekly and there is no historical on-time performance for my flights as the times move ever-so-slightly.

    I remember doing the ORD-BOS route pre-merger. Flight 545 got me home. The later was 547, earlier was 543, then 541, and so on. The reverse route used even numbers: 540, 542, etc…

    1. I WISH… Oh so wish United would bring this pattern back!!! I do ORD-DCA-ORD all the time, the flights used to all all be in the low 600s…608, 610, 612 went one way in order of the flights that day, reverse was 609, 611, etc.

      Also…oddly they left 881 and 882 alone…they are same flight numbers used back when UA had the predictable (and now missed DCA flights). Yes, it is international flights…since international flights tend to have better on-time rankings. Think I might be joining the conspiracy theorist that UA is changing the domestic flight numbers to impact DOT and reservation system on-time percentages shown.

      If it is purely to assist internally with managing fleet types then United’s PR has yet another example of how they did not do right for the customer and needs to push for some changes internally.

      Don’t be shady United…we will like you better if your are straight up with us…really.

  5. As was mentioned above, changing the same flight (time/city pair) with a different number means it shows up as N for new so will not show the bad on time rating of say 3 if they keep the same number all the time.

    When I was at TWA the same flight number OUT of a hub was kept the same but the flight number into the hub could be different. Example in fall/winter flight 123 could be SEA-STL-MCO but spring/summer flight 123 could be DEN-STL-MCO. They did this to help ground crew at hubs to always know flight 123 baggage always went on the STL-MCO flight to help keep baggage from being miss routed if they were to always be changing a flight number out of a hub to a different city.

    Funny, but I’ve noticed non-U.S. carriers will keep the same flight number in the same market almost forever, but U.S. carriers seem to be the ones changing them all the time. So maybe the fooling the on-time record keeping system isn’t as far off thought as it might seem.

  6. I am curious how it affects through flights / change of gauge / same flight number connections. For example, UA might schedule flight 001 for FLL-IAH on a 737 then IAH-CDG on a 777. If I searched FLL-CDG, it would come up higher in search results, even though it is not a non-stop flight because many computers read it as one flight with a stop, not 2 segments (even if you have to change planes). This in theory, allows UA to exploit different city pairs on different days.

  7. I’m shocked, SHOCKED I tell you that United did something for their convenience without considering its impact on their customers. Its probably the first time in their history that they’ve done something like that.

    I’m curious if there is more that can be said about airlines varying their schedules by day.. I remember reading the time tables back in the day, and usually M-F was the same schedule, with Saturday and Sunday having some variation. Sometimes you’d get a bit of variation on Friday as well, but nowhere near what I hear is happening now..

  8. Wait so Are PMUA crews not flying with PMCO still why does this feel like Cactus US Air all over again? But so okay that’s why United has such weird flight numbers its to help them but accidentally confuses passengers who fly a whole lot

    1. Jeremy – They have a joint contract and single seniority list so this is nothing like that America West/US Airways merger. (That couldn’t happen again anyway thanks to changes in legislation.) I know that some fleets are fenced off from the other side for a certain period of time (like the 787 and 747), but I would think that they are indeed flying together now. It’s really just about fleet type for the flight number changes.

  9. Hello,

    The true reason may be simpler than that. Flight statistics. Many passengers review the history of a flight being on time, and if the flight numbers are changed often there is not a lot of data. UA brings up the rear in on time performance, and by changing numbers this improves the likelihood of a passenger purchasing the flight.

  10. I’m OK with flight numbers changing day-to-day–I just wish they would stick with a flight number once the schedule is published. I can’t tell you how many times I get e-mail notifications from AA with flight number changes for flights booked 2-3 months in advance. It drives me crazy.

  11. UA can provide some very good service. It can also be a very aggravating carrier. Flight numbering, marketing flights such that things can be called “direct flight” just because the flight number doesn’t change (of course, you have to change planes but UA doesn’t care). “Change of gauge” marketing.

    Of course, I’ve written numerous letters to UA, OAG, and DOT about this and how I believe UA is engaging in deception. Play around with the flight numbers and “bingo, you can legally get around anything you want regarding the need to change planes, something you know is an inferior service compared with non-stop service. Just avoid saying it involves a plane-change, or develop a system of asterisks with lawyer-written abbreviated script (disclosure statement, they call it). Hey, keep the customers guessing. Get the sale! Particularly if the sale takes a seat away from the competitor that might be operating more consumer-friendly.

    With UA, it’s like playing “whack-a-mole.” Fix one thing and they’ll get the lawyers to come up with an alternate you’ll probably find worse.

    I wrote that it’s nuts to list flights in the OAG and call them “direct flights” when it makes no sense. “Direct flight:” BWI to Philadelphia, change planes in Houston and LAX. Dulles to Pittsburgh, change planes in LAX and Houston. Well, you see the flight operates with the same flight number throughout. Have to change planes? Who cares! “Direct flight!”

    I think my letter helped get that moderated. But, if you look up UA 1259 for Wednesday, BOS to SLC, it’s still listed as a direct flight, evey though you have to change planes in SFO. Service from BOS to PIT, change planes in ORD. (If it takes business away from JetBlue or DL, it must be OK!)

    Then, I wrote that it’s crazy to market so many one-stop flights, no indication that you would have to change planes at that stop. Would you have know that when you bought the ticket? No way! So. the flight makes a plane-change despite what you may have thought. Tough! Probably something beyond our control, says UA. Oh, on 50 percent of these flights? Well, it looks like there are fewer one-stop flights being marketed. Now, they’re all marketed as change-of-gauge, still “direct flights!”

    So, I believe UA knows exactly what it is doing numbering flights. It’s for marketing gain, to hell with the customers. To UA, there is no difference among non-stop, one-stop, change of plane or connecting service. Will it involve a plane-change? Who cares. This is the way we operate.

    Of course, UA can operate any way they want. Number flights whatever. But, be truthful as to how the service operates, principally when it comes to the need for plane-change. If DOT doesn’t stop it, nobody will. Move to another carrier? In today’s concentrated airline environment? Not sure that is going to work anymore.

  12. This isn’t the first time this question has been asked. Several years ago someone on this board asked why all the different flight numbers on UA on what is basically the same flight day in day out. My comment was this was an artifact of the merger-CO was doing this Flight Number Tango for years, and was carried over after the merger. Why? who knows-maybe to confuse the public, marketing, what ever. Or what I said several years ago-maybe they(UA) are nuts. I’ve also noticed this tactic is starting to be used more and more by both DL and WN. AA on the other hand, well Flight 75 may have changed equipment, takeoff and landing times thru the years, but it is still LAX-IAD, and has been that way for at least 20 plus years.

    1. “My comment was this was an artifact of the merger-CO was doing this Flight Number Tango for years, and was carried over after the merger. Why?”

      Because CO leadership brought a whole trunk of sacred cows north to Chicago, and attempted to paste them onto the merged carrier. “We weren’t bankrupt, so our way of doing things is clearly the right way. Work hard, fly right!” The airline is still suffering the effects of that kind of thinking today.

  13. I guess I’ve been aware that UA has been playing some Flight Number Games for a couple of years, but I had no idea that it was as common as cited here. WAG, two-cent’s worth is that the real reasons behind the Number Games include ALL of the above to some degree. I also think the MAJOR reason is their lame attempt to BURY some truly horrible performance data. UA may not fool DOT, but they sure do Piss Off a bunch of their customers! Currently, if necessary to call UA agent, I begin by referring to, ‘your 7:46 AM flight from ABC to XYZ, and avoid using the Flight Numbers. And, as one commenter noted, if the ticket is issued more than a very few days before departure, the changes generate a short ton of change notices, all of which have to be toted along in some form (paper or digital) on the day(s) of flight.
    If I have to say this – Yes YOU, UNITED, this is but one of several reasons that I avoid your airline as often as is reasonably possible; you’ve become too damn difficult to deal with! Unfortunately, UA’s regional service from/to my regional airport is slightly better than the other two so in some instances, I have little choice. When given a *reasonable* choice, I begin and end trips with regional carriers affiliated with a major OTHER than UA. Thanks for the great answer, Brett.
    P.S. (And, to a large degree like identifying the assigned aircraft type, I think UA blew some smoke where you probably do not need it. Let us never forget that the IT systems and data available to UA’s in-house staff in all departments ‘automagically’ display a lot more detail that we will ever see. They simply no not need flight number encoding to identify and aircraft or even a specific airplane. Balderdash.)

  14. I’m amazed at the number of people who think this is United’s conspiracy attempt to hide poor operational performance. That gives them way too much credit. I think it also assumes a lot of people actually pay attention to the stats (outside of DOT reports, which as mentioned, do account for flight number changes). I’d actually be surprised if a lot of people look at that.

    1. it’s not UAs… it’s the Regional’s game.

      Explain this: To my airport, we have 6 basic flight numbers… pretty much every day, the flights switch flight departure times but the numbers stay the same.

      Once upon a time, it used to be that 6011 was the 4PM inbound and outbound, 6012 was the 6PM inbound/outbound, 6010 used to be the inbound/outbound for 12:30. 6009 was the 10AM.

      Today, 6011 turns into 6009 10am, 6012 turns into 6010 12:30, 6009 inbound (new plane) and turns into 6011 for the 4pm, and 6010 (different plane also) comes and turns into 6012 for the last flight.

      However, tomorrow 6012 is the outbound 10am, 6011 is the outbound 12:30, 6011 is the 6pm, and 6010 is the last flight.

      Then the next day, it changes again. It’s a shell game. Even more cement to the game is that the first flight out and the last flight in… have typically stayed the same number for this regional operator when it operates the kickoff/terminator. Why? The first flight out is rarely delayed/cancelled. The last flight in, when it starts becoming chronically late, it will randomly switch to a new number for a month (throwing off statistics) and then go back to the old number again. Rinse, repeat.

      You tell me what you think about this? There are a lot of coincidences for it to just be “planning”.

      On the other hand on the DL side of the airport, the numbers don’t play this shell game. Typically over there, when the numbers change, the operator changed.

      1. Also, with the flight number crap, comes the monthly schedule change +/- 31 minutes.. there’s your DOT throw-off data.

        1. I’m surprised the DOT just doesn’t tweak the data reporting a bit. Split the day into 12 equal parts. (12 am – 1:59am, 2 am – 3:59 am…. 6 am – 7:59am, 8 am to 9:59 am, … 4 pm – 5:59 pm, 6pm – 7:59 pm etc.) and group all the flights between any given two city pairs in the same bucket, all the flights in that bucket get assigned the weighted average for the bucket. This’d probably be more fair and get around any of this potential system gaming stuff.

          The other thing I’m curious about is how quickly do the airlines have to report a flight’s disposition to the DOT and how granular is it? Do they report that flight 724 was late 25 minutes on May 1, but arrived within 14 minutes “ontime” every other day that week? This could be a way for a GDS to differentiate itself by providing some better info about on-time flights etc.

            1. CF – what is the lag time? A week? A month? A quarter?

              Sent from my computer that moonlights as a phone. Please forgive any misspellings or terseness.

            2. Nick – Not sure about DOT specifically, but I can see the data within a day when I look at masflight.com. It’s very quick.

      2. Adam – I’m trying to follow what you’re putting together here, but I don’t see these in the corresponding schedules. I’m guessing you’re in Green Bay, but I don’t show 6009 or 6010 as valid flights. For 6011, I do see how it operates at one time on some days and another on others. Regionals are a lot tougher because they have to dedicate flight number ranges to specific regional carriers. That means there’s really even less to play with in terms of give and take. But clearly, this is a goofy way of doing it. Looking out into the new schedule, 6011 is consistently the 11a departure.

        I really don’t buy into any of these theories that United is doing this to game the system. I think they honestly aren’t thinking about the customer at all.

    2. CF: Actually, it’s right on United’s booking site. When you get the screen to select flights, it has a link for each flight “See On-Time Performance.” When you click on most of them, you get “There is no recent record of delay and cancellation percentages for this flight.” So while that may not be United’s motivation, it is something that anybody who books on their website has easy access to. I check on-time ratings for flights if it is available on the booking site, especially when flying TATL and there is only 1 daily or sub-daily to my destination. I don’t like killing time at airports on a connection, but rather kill a few hours than risk a misconnect on a flight that is never on time.

  15. Thanks for this dorky analysis. :) I’ve noticed it when I’ve been looking to take a flight — or change a flight — on a slightly different day, and the flight number was different. I thought it was odd but, in the scheme of life’s mysteries, not something I needed to look further at. Otherwise, the only time I ever look at flight numbers is when I need to plug them into the websites to see if the flight is running on time, or I want to look at the upgrade list. It’s faster to know the flight number than enter in the city pair/departure time info.

  16. I’m in that small group of people who consistent flight numbers matter for. UA has driven us crazy since the merger, and we’ve occasionally had to buy a plane ticket for someone when we flubbed a random flight #/time change and not gotten people to the airport on time. Can’t tell you how much I’m looking forward to that April schedule!

  17. United can’t do anything right in my opinion….they ruined Continental, getting rid of people left and right….read today where they are going to contract out and layoff people in Oklahoma, i feel bad for those affected….before long United will be all contract employee’s it seems like….so with flight numbers changing so much, United can’t even figure out how to do it right…..i remember the days when timetable’s listed the major airline and the associated carrier’s they connected with….the major had it’s set of number’s and associated carrier number one had flight number’s 1000 to 2000, associated carrier number 2 was 3000-4000…..it also use to be where wide-body flights had 1 or 2 digit flight numbers….gone are timetables, flight numbers you could depend on because some airlines used the same flight number for a flight all the time…simplicity is gone, and a desk jocky needs something to do, so they screw with the flight numbers….

    1. Please remember that Continental Management are the ones running the airline, they kept the United name due to it being better recognized worldwide. So your comments are blaming the wrong people.

  18. I did find out that the $200 fee for any changes to an itinerary doesn’t apply in this case; or at all to any airline, only changes initiated by one of their customers. If they had to pay the same amount as their customers, the fee would go way down, and it would happen a lot less often.

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