What do you do when there's no more carry-on room?
Flying is bad for the environment. Don't do it.
That being said, if you do fly (cough), you may have experienced a common conundrum: the overhead bins fill up, and the flight attendants asks you to put your backpack under your seat.That wouldn't be such a big deal, but you overstuffed this backpack for your trip to avoid paying luggage fees. Now you're doomed to cramming the backpack "under" the seat in front of you and squeezing your legs into the tiny space left.
You dutifully sit like a magician's assistant crammed in a box and spend hours wishing you could stretch. When you stand up, your legs fall off. Now how will you go on that walking tour?
I understand; I've been in this situation many a time. And I finally found a solution.
1. During takeoff, keep your backpack under the seat in front of you like the flight attendant says, so the plane doesn't fall into a black hole.
2. After takeoff, pull the backpack against your chair.
3. Drape your legs over the backpack like it's a leg rest.
There: You've just turned your backpack into a recliner chair. It's surprisingly comfortable; you can stretch your legs out just as much as you could without a backpack. I'm no doctor, but I imagine giving your legs room to breathe is healthier than keeping them crammed in front of you.