I was on air china alot this summer and realized that on narrowbodies, their lettering goes ABC-JKL, and always wondered why they just skipped 6 letters? After a few widebody trips, I noticed why, it really makes for consistent seating letters.

A is always left side window (universal to all planes)
B is always left side middle (where available)
C is always left side aisle

center block only applies for widebody flights:
D is always center block left aisle seat
E is always a center block middle seat
F is used only for the super-middle seat in a center block of 5 (F for FAIL) as well as the middle seat in a center block of three seats (still FAIL on 767s)
G is always a center block middle seat
H is always a center block right aisle seat

J is always right side aisle
K is always right side middle
L is always right side window

When planes get swapped out, especially with the 777s going from 2-5-2 to 3-3-3, wouldn't air china's system really help with swaps?

the 2-5-2 could be:
AC-DEFGH-JL

The 3-3-3 would be:
ABC-DFH-JKL

this way, only E and G folks will get moved from the 2-5-2, and likely into the B and K slots in the 3-3-3.

This way, if you picked a C, D, H, or J seat, you'd be assured of an aisle, regardless of which config.

and if ur flying in coach, you can stay away from the F seat, which almost always stands for "FAIL"

further examples of lettering for different configs:

1-1
A-L

1-2
A-JL

2-2
AC-JL

2-3
AC-JKL

3-3
ABC-JKL

2-3-2
AC-DFH-JL

2-4-2
AC-DEGH-JL

2-5-2
AC-DEFGH-JL

3-4-3
ABC-DEGH-JKL

1-1-1
A-F-L

1-2-1
A-DH-L

2-1-2
AC-F-JL

2-2-2
AC-DH-JL

i think that's all the configs u can come up with, unless some charter company crams 11 ppl in a row:
3-5-3
ABC-DEFGH-JKL


wouldn't this consistency really help?

Another thing air china does, Rows 1-10 are always reserved for the first class cabin, regardless of how many numbers actually get used. Rows 11-30 are for business class, regardless how many numbers they end up using. Row 31 and up for coach. This way, if you got 31C, you know you're in coach bulkhead aisle, regardless of which aircraft you're on...

I think UA and the rest of the domestic airlines could learn something from air china here in the name of consistency. This way, only middle seat folks get moved in case of swaps (smart couples would book window-aisle anyways, and swap with whoever ended up in the middle seat once onboard...)