Why Do We Fly In High Clouds? (Ask Cranky)


This is a bit of a strange Ask Cranky in that it’s actually a question I’m asking myself. To pilots, this is an elementary question, but I’ve had this conversation with other window-seat lovers and they Ask Crankywant to know the answer as well.

I’m wondering why it is that when there’s a high cloud layer, it seems like we often sit in it instead of above or below.

My guess was that it’s likely to be less bouncy within the cloud layer itself, but I really don’t know.
Brett S

Seems slightly insane to ask myself that question, so instead I asked a commercial pilot friend of mine to give me an answer fit for publication. Here’s what we had to say:

Altitude selection is generally based on the winds and the weight of the aircraft, and is independent of where the cloud layers are. Higher altitudes allow more efficient operation, but they may not have the best winds, and may also not be within the performance capabilities of the aircraft at a given weight. For long international flights, the aircraft normally climbs every hour or two as weight is reduced. Sometimes, a particular altitude may be chosen for a certain period of time to avoid forecast turbulence, but that too is normally independent of cloud layers. During the actual flight, if it is turbulent within a cloud layer, the crew may request a higher altitude to get on top, or perhaps a lower altitude to avoid being in the tops of a cloud layer (which can be more turbulent than within the cloud itself). I don’t know of any other scenario where it’s smoother within a cloud layer than outside of it.

All of that is assuming that the clouds are not associated with thunderstorms. Thunderstorms are always avoided, generally by flying around them visually or using radar.

In other words, it’s just bad luck. I love looking out the window when I fly and it seems like we’ve parked ourselves in a high cloud layer a lot on recent trips so I can’t see anything. Like this on the way home from DFW:

Sitting in a Cloud Layer

On that flight home, the captain said winds were very stiff at lower altitudes so we were going to climb above them. But we were cruising in the tops at 32,000 ft. Why not go to 34,000 ft so we could have a nice view?

My friend said there could have been a few reasons on this particular flight.

  1. We could have been too heavy to climb higher (and though he doesn’t fly the 737s, he said he’s heard they can’t always get as high as you might like).
  2. It could have been that the winds higher were, in fact, stronger on the nose so we wouldn’t want to slow ourselves down by moving.
  3. There could have been traffic that prevented us from climbing higher.
  4. The pilots could have just not cared to climb since it wasn’t all that bumpy.

Apparently, my view out the window is not the primary concern. Who knew?

Kind of a silly post, I know, but it’s something I’ve pondered many a time since my favorite thing to do on an airplane is look out the window. When you’re in the clouds, that’s just not fun.

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33 comments on “Why Do We Fly In High Clouds? (Ask Cranky)

  1. I know that 2 jet aircraft approaching head-on will essentially appear out of nowhere due to combined speed, but isn’t there also an argument that by cloud reduces visual capacity.

    Should not be necessary with all the sophisticated gadgetry, but by flying outside clouds, a pilot has a better chance of being able to look out the window and see if there’s any kind of risk of collision. Yes, this is ATC’s job, but it never hurts to be able to use your own eyes to verify what the computer is saying.

    I’m thinking also of cases involving a military aircraft in international air space that may have turned its transponder off (yes, I live in Europe and know what Tu-95 aircraft have been doing)

    1. From my experience in a flight deck, no matter how good the visibility, it’s near impossible to spot a head-on aircraft at altitude early enough to maneuver and avoid.

      1. As a former captain for an air carrier, I agree. By the time you spot an oncoming a/c it’s virtually impossible to avoid a head on collision.

    2. Except for some very unusual exceptions, All aircraft above 18000 feet are under Instrument
      Flight Rules (IFR) and are under ATC control. Thus they are separated laterally and vertically.
      So visual separation is not a factor (ie; looking out window for opposite direction traffic).
      Also on heavy travel routes, it is often one way traffic (Everyone from NYC to ORD for example).
      Most often reason for not getting an altitude change during my flying career was traffic

      1. While perfectly true that ATC is responsible for maintaining separation (V&H) at/above FL180, the ‘ultimate’ responsibility still rests with the crew – meaning the captain. The mandatory TCAS systems help, but gizmos fail at time and the responsibility still rests with the crew. (Funny/strange, that providing separation is ATC’s principal responsibility up there, yet they are never held accountable for errors or even colossal failures. The government protects itself with LAWS; the public sector cannot make LAWS.) In the end, I agree with @Donald that most altitude requests declined by ATC are based on other traffic. In simple terms, one general direction moves at even numbers like FL380 and the other direction at odd numbers like FL370. If a controlled flight wants to move from FL380 to FL360, obviously, crossing FL370 is necessary. If there is opposing traffic at FL370, ATC declines the request, usually appending ‘traffic’ to their refusal. Most lateral moves, typically to fly around a nasty-appearing cloud formation, are much easier to grant because most aircraft stay close to their currently assigned altitude. Seeing a ‘conga line’ of aircraft following each other *around* a storm cloud is common. -C.

  2. Back when I was a commercial pilot, altitudes were assigned by Air Traffic Control. The company flight plan altitude took into consideration such things as turbulence, head/tail winds, and fuel savings. During our clearance delivery message from ATC, we were told to EXPECT our requested altitude 10 minutes after departure. BUT, our final altitude was usually predicated on conflicting traffic. We could always request a new altitude en route, but once again we were constrained by conflicting traffic. Hope this helps.

  3. From a Dispatcher’s perspective, I can tell you that cloud top or bottom is almost never a consideration, the exception being thunderstorm clouds (go on top or go around). More so, unless it is convective activity, information on tops of clouds is hard to come by. Easier to determine and plan for: turbulence. Plus, smooth rides benefit everyone on board vs just window watchers.

  4. So were you cranky that you couldn’t see the ground? It is fun to see the landscape below, especially if you can identify landmarks. Love seeing cities all lit up at night too. Unfortunately those pesky clouds get in the way of our entertainment.

  5. As far as I have always understood, even though we would be in the clouds and the pilot could not see through the fog, they would still have the route charted on their GPS they can still navigate the flight perfectly fine following the coordinates. The reason maybe the flight would probably try to go higher is to avoid the winds going on below. I know when I have taken flights when there is wind, we sometimes go higher in to the clouds.

  6. Altitude used to be determined by direction, odd was for west to east, and even for east to west. Also, the best air could be above 40,000 feet, but most pilots who drive airplanes that can go that high do not like it because that airspace is not under ATC control (uncontrolled)

    1. Controlled airspace goes to 60,000 feet. Most airliners are not capable of flying above 40,000 and if they can, it may take a while to get there. Another important factor is safety: if you have a traffic advisory and are instructed to climb, it doesn’t help if you’re already at your service ceiling.

      1. Another detail is above 40,000 (or maybe its 38,000) one member of the flight deck has to have their oxygen mask on at all times, because in the event of depressurization at that altitude the pilots may not have enough oxygen to provide useful consciousness to put their oxygen masks on.

          1. I’m not a pilot, but I’d figure it still is in force. People haven’t evolved that much over the past couple of years.

  7. I don’t like when you see near by clouds with bursts of lightening in them and then you start flying in clouds, I wonder our cloud will have lightening too.

    1. You should read up on how lightning works and how airliners are made to safely take strikes. Happens all the time. Also there is no “e” in lightning. An education would do wonders for timid flyers.

  8. Flying along in a great big ol’ airliner, one flown by a well-trained, experienced crew, a cabin where the the window row actually has a window, for me is one of life’s great joys. In the clouds, then out, on top, just below. Of course, the enjoyment for me is enhanced by being able to hear the communication between crew and ATC. [Folks at UA…Channel 9 is something I’d pay a little extra for!]

    I must have taken a million pictures over the years of this cloud and that, a brilliant display of lightning off in the distance, all the while me wondering why we doing this, doing that. A mystery for most of us, but a joy to tryi and figure out….with seat belt on!

    And then, there’s flying along at 5, 6 thousand feet in a little 2-engine, 9-pax EAS-airline plane, where you can see all the weather in front of you, above you, below you, behind you, off both wings. Oh no, we’re heading right for that big, fluffy cloud! Yes, I can see he or she saw it, but…! And then there’s that cloud layer, right at our altitude, a little rough, but, well, thank goodness, FAA still requires at least one crew member in each flight and he or she can feel what I’m feeling! Is there a bumpiness gauge on that panel?

    If you ever find life depressing, get yourself up into the air and enjoy what He or She made for us to be in awe of!

    1. I concur. However regarding Channel 9: In yesterday’s post you expressed your consternation at a la carte pricing and add ons, and a distaste for the modern environs of flying.

      But I agree with your prose; flying for pleasure truly does lift the spirits. (Unless of course it’s on Spirit.)

      1. Gawd! Is UAL now charging for access to Chnl 9? I heck with them; I’ll take my own radio along. (But then I rarely fly UAL and take the radio anyway. With my own pre-flight planning I can cat most freqa programmed ahead of time and if I pay attention, I hear most freq changes for my flight. Of note: Transmitting on those frequencies is a serious, major violation and don’t even think about it! **Listening** is perfectly legal and go for it. Even with pages of notes and freq. numbers, I’ve been asked to cease only once. I did do an raised hell later and got an apology. (Never – NEVER argue with flight or cabin crew!!)

  9. Meanwhile – DL 1086 from Atlanta to La Guardia banked left apon approach & skidded down the runway & came to a stop at a fence at the edge of Flushing Bay.

  10. I am a Dispatcher at a major. Jet engines are more efficient at higher altitudes. It would cost about $500 (according to my flight planning software) to operate a large jet at FL350 vs. FL310 from LAX to MEM. While that might not sound like a big deal, if you average that cost over the almost 47,000 flights a week American operates, that’s over $23 million dollars. THAT is why pax carriers don’t care so much about your view.

    1. That is…..the cost would be $500 higher to operate down low. It’s all about the cost of the flight, and nothing to do with the clouds and your view.

      1. Maybe airlines should make a good view an al la carte option. $100 a passenger only implemented if ten passengers buy it, and it’s a refundable option.

        Who will do this first? My money is on Spirit.

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

        1. @Nick. Hilarious. What is next? Perhaps they will attempt to charge extra for a seat/space that actually go CLEANED during the last extended turn. One of my biggest bitches these days is that some carriers, even long haul majors, seem to clean only weekly. It varies, but some cabins are FILTHY. Best best is first flight of the day for the hardware, but even then…

  11. It is nice to be able to always fly free of clouds, but sometimes circumstances do not permit this such as weather and also air traffic conditions. Planes are controlled by four forces (Lift, Drag, Thrust, and Weight). Weight can vary depending on the aircraft, but I never considered the fact that the amount of fuel would be a determining factor and as fuel is consumed, weight is reduced, and a higher altitude is possible if all other factors check out. Using visual confirmation to avoid collisions is not possible or efficient. Commercial airlines must fly by IFR (Instrument Flight Rules), not VFR (Visual Flight Rules). We cannot always have the conditions that we would like. Such is the nature of air travel.

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