I use my osprey porter 46 on budget and legacy airlines in Europe all the time, no questions.

The shape is great for packing, and certainly totally comfortable to carry with, say, 10 kg in it, no problem.

I have a number of other daypacks, schoolbags, shoulderbags, I sometimes use, depending on the trip, but for maximizing carry-on, then is my choice.

I've had it for a couple of years and have no concerns about materials, all feels very sturdy still. For getting checked, you'd pack away all the straps - this to me is the main difference between backpack and travelpack: travelpack is prepared for checkin by having the option to pack away the shoulder/hip straps to protect them.

DanishFlyer