Occasionally, aircraft with a seating structure of 2+2 may letter the seats as ACDF to keep with the standard of A/F being window and C/D being aisle on short-haul aircraft (which generally have 3+3 seats).
The convention seems to be that the window seats will be A and F, and the aisle seats C and D. So, where there are only two seats on each side, B and E are not used.
Occasionally, aircraft with a seating structure of 2+2 may letter the seats as ACDF to keep with the standard of A/F being window and C/D being aisle on short-haul aircraft (which generally have 3+3 seats).
Many airlines use nearly all letters of the alphabet to allow finer yield management. Nevertheless, certain booking codes have retained the same meaning across most airlines: Common Airline Classes of Service Codes F - First Class, J - Business Class, W - Premium Economy, Y - Economy/Coach.
An “A” or “F” mean first-class treatment, while a “B” often means you're more likely to get upgraded than if you have a “Q” or a “Y” on your ticket—the latter two are typically the cheapest economy fares.
Occasionally, aircraft with a seating structure of 2+2 may letter the seats as ACDF to keep with the standard of A/F being window and C/D being aisle on short-haul aircraft (which generally have 3+3 seats).
Aviation always looks to maintain a global uniformityIn a single-aisle aircraft, with a 3-3 configuration, the common practice, and understanding is that ABC are window, middle, and aisle seats respectively on the left side of the airplane and DEF are aisle, middle and window seats apiece on the right-hand side.
On the most basic level, the person in the window seat has control over the window shades, and shouldn't need permission from the person in other seats as to how the window shades are kept. The person in the window seat can, within reason, decide if they want the window shade opened or closed during the flight.