Although I have nothing but bitter things to say about the space available for humans on this plane, Chloe seemed to have an okay flight.
Delta’s 757 (-300 series) planes are divided into First Class and Economy Class. I only caught a glimpse of First Class as I was walking through, but the under-seat spaces didn’t look impossible for an in-cabin dog. Economy Class has three seats on each side of the aisle, except for oddball Row 14 (which is an exit row anyway, so off-limits to travelers with pets).
Your best choice on this plane is a middle seat. The under-seat height (once you squish the life vest packet upwards) is 10 inches. As is so often the case, the depth (measured from just below your seat pocket to just behind the feet of the person in front of you) is 17 inches. The width of the under-seat spaces, measured left to right, is 17.5 inches for the window seat, 19.5 inches for the middle seat, and a mere 15 inches for the aisle seat.
This post is part of an ongoing series recording under-seat measurements of the various planes we fly on. Keep in mind that most domestic and international airlines have rules about the maximum size of in-cabin pet carriers they allow on board (see Dog Jaunt’s handy charts under the “Taking our pet on a plane” tab above).