Thank you both ninjastyle and firstglobal for the links and real-world example, respectively.
After reading the above threads, I found this
Southwest.com link detailing the under-seat dimensions (listed below).
The under-seat dimensions are as follows:
Window Seat: 19"L x 14"W x 8.25" H
Middle Seat: 19"L x 19"W x 8.25"H
Aisle Seat: 19"L x 14"W x 8.25" H
It seems like 8" is the max depth I should shoot for. I'm shooting for that middle seat too, look at the room under there!
It's weird hijacking my own thread, but I'm open to bag/backpack suggestions if anyone has any? I tend to carry a 15.6" laptop, projector (~11x8x3), a few days worth of clothes (~14x4x4), along with the various essentials (cables/chargers/basic toiletries/etc.). Given that I'll be flying quite often (at least once a week), I'm starting my search with TSA/Checkpoint-Friendly backpacks. I'll be testing out the
ecogear Rhino II Laptop Backpack this week (18" x 12.5" x 7"; 2000 cu. in.); although if I could I'd prefer something with a little more volume.
Thank you.
EXTRA:
I took this opportunity to look up the maximum pet carrier sizes (which should be close to maximum under-seat dimensions) for the few other airlines that I fly, in hopes that others may find it useful.
US Airways
hard-sided carriers up to 17" long (43 cm) x 16" wide (40 cm) x 8" tall (20 cm)
soft-sided carriers up to 17" long (43 cm) X 16" wide (40 cm) X 10" tall (25 cm).
Frontier
Airbus A318/A319/A320: 24" length x 15. 5" width x 10" height.
Embraer E190: 18" length x 13.5" width x 10" height.
Embraer E135/E140/E145: 17" length x 12" width x 10" height.
Bombardier Q400: 17" length x 15.5" width x 12.4" height.