Went ORD-SEA on American's redesigned w/internet boxes 737. Configuartion is 3-3 and we always take cross aisles. I am Platinum and wife is Perma-Plat/2 million.

Traveling with our dog, a six pound Peke, whose Snoozer carrier fits under all seats, even on Eagle flights. Guess what, not on the newer 737s. Had to switch to middle seats on both outbound and return, because internet box takes up too much room to allow carrier under the seat. FAs were very surprised also, especially since we always make a reservation for the dog (and pay the fee at check-in).

So, if you are traveling on an AA newer 737 with an on-board pet, don't count on that aisle seat, that you paid a premium for.