Originally Posted by ClipperDelta

LGW-JFK is operated by a 767-300ER, not a -400.

The 763ER fleet is in transition now, i.e., they are being reconfigured to add 19CDE so it's a crapshoot in terms of whether you will end up with a reconfigured plane or not. If you have 21AB already, I would suggest sticking with it rather than taking the chance...

Right now, by default all 763ER flights (through March) show seat maps with no 19CDE; however, more and more 763ERs are getting 19CDE added so there is a good possibility that by March, your 763ER may end up being a reconfigured one...