I started this series in December 2009, when I wrote a post about the space available under seats in Southwest’s 737 (-700 series) planes. Southwest had published its under-seat dimensions (the only airline I know of to do so), but I felt that more info would be helpful when you’re trying to figure out which seat has the most space for your in-cabin pet.
Keep in mind that this info should not be confused with the various airlines’ stated maximum sizes for in-cabin pet carriers! Jet Blue, for example, officially requires that an in-cabin carrier be no more than 8Hx17Lx12W, even though (as you’ll see below) some of its seats could accommodate larger bags. Take a look at Dog Jaunt’s handy guides for the major domestic and international airlines.
Please also note that it makes a difference which airline you’re talking about — JetBlue’s configuration for its A320 planes, for example, is very different from the configuration chosen by Virgin America for its A320 planes. No matter what plane or configuration you’re faced with, however, you’ll never be able to sit in an exit row with your in-cabin dog. I’ve sat in a bulkhead row a couple of times with Chloe, when it had those cut-outs and I could put her carrier under the seat in the next section in front of me — but that was a long time ago, and has never been allowed since, so you shouldn’t get your hopes up for the bulkhead.
I travel a lot, but you travel even more than I do. If you happen to be carrying a tape measure, please send me the under-seat measurements for planes that aren’t yet on this list! Get way down on the ground so you can see any electronics boxes or life vest containers that are tucked under the seats, and for each seat in the row measure (1) from the ground up to the bottom of the seat or the bottom of the hanging object, (2) left to right, making sure you notice any rails that narrow the space even if they don’t extend to the floor, and (3) front to back. Notice whether all of the rows are the same, or if there are variations. Thank you in advance!