If you flew through San Francisco (SFO) yesterday, you may have noticed things looked a bit different. No, no. It’s not that the planes can actually run on time when there’s a cloud in the sky. (I mean, please.) The big change is cosmetic. All gates changed their numbers. Nothing like a good gate shuffle to get the blood pumping.

The old system of numbering at SFO was to use straight-up numbers increasing in a counter-clockwise manner. Gate numbers started in Terminal 1 and then topped out with gate 90 in Terminal 3. This has been somewhat problematic for awhile.
When the International Terminal opened in 2000, those gates numbers took on a modified numbering system. They still had numbers that fit into the overall system, but now they added the concourse letter in front. At least, that’s what happened officially.
When I flew JetBlue up to SFO in May of this year, I landed at gate A11B. Not all airlines used the letters however. United flight 837 took off from gate 97, or so United said, on Tuesday. That’s technically gate G97, but United didn’t bother with the letter.
The opening of the the new Terminal 1 had to be the catalyst for the change. The old twin banjo concourse in Terminal 1 (the non-Delta gates) had 22 gates numbered from 20 up through 38 (using A/B as needed). The Delta gates began at 40. But the new concourse has 28 gates. They could have just gone crazier with the A/B designations, or they could re-number everything. They chose the latter.
As of yesterday, every single gate at SFO has officially been re-numbered. Now, the terminals become somewhat irrelevant and instead, it’s the concourses that matter more. As was the case in the International Terminal before, each gate will start with the letter of the concourse. But instead of having the numbers increase around the circle, each concourse will now start with gate 1. Here’s the map with before-and-after numbering.

A1-15 (International Terminal) – Alaska (Intl), Frontier, Hawaiian, Sun Country, and several International carriers
The old A gates are the closest to their original numbering, but this re-numbering allowed SFO to get rid of the A/B designators so it’s sequential throughout that concourse. As an aside, I would imagine that the remainder of the domestic airlines will move into B once that work is done.
B1-27 (Terminal 1) – JetBlue and Southwest
The new concourse in Terminal 1 never had old gate numbers, since, well, it’s new. But these B gates replace the old gates 20-38. Note that all those in red have yet to open.
C1-10 (Terminal 1) – Delta
Delta’s gates are due to eventually be re-done, but for now, they just get a number change. Eventually there will be one new gate added to C (technically between B and C) once the construction is done.
D1-18 (Terminal 2) – Alaska and American
This is the old international terminal that was re-done as Virgin America’s home. It will eventually become all Alaska’s, I believe, and American will move into Terminal 1.
E1-13 (Terminal 3) – United
These are the old gates in the 60s that American used to use before moving into Terminal 2. After American moved out, United moved in and fixed the place up. This will also include 70/71A/71B.
F1-22 (Terminal 3) – United
The meat of United’s operation is concentrated here in what used to be gates 72-90.
G1-14 (Terminal 3) – United (Intl), its partners, and some international cats and dogs
United continues to use the G gates, but the gates now have lower numbers than they did in the old days. For example, G92 is now G1.
This seems like a lot of effort, but will there be enough benefit? I’d think it probably is worthwhile. After all, the use of A/B designators got somewhat out-of-control as they tried to shoehorn the number of gates they had into a fixed set of numbers. I count more than 30 in the old system, including a couple of C gates. Those are ALMOST all gone. Inexplicably, gate 73A becomes F3A, the only one to use that in the entire airport.
This change also eliminates some of the quirks of the old numbering system. For example, 72 and 81 were about as close to each other as 72 and 71B or 76A and 81. A change in the first number made people think it was a different terminal (as is the case in Los Angeles) even though it wasn’t. So this should reduce confusion.
This is similar to what Honolulu did last year, and in an environment where the number and location of gates can change, it does make sense. There is more flexibility when you start with the concourse, because then you can have up to 99 gates without needing to re-number. And there is no chance any concourse is going to have 99 gates.
I’m sure it’s been disorienting for travelers who didn’t realize the change was coming, but as with everything else, people will eventually get used to the new system.