Originally posted by LeDave What backpacks do you guys recommend that are able to carry-on in airlines?
It REALLY depends on your needs.
For me the best camera backpack is the Mindshift Gear Horizon. But I'm a hiker. The Manfrotto Off Road Hiker is a close second.
For someone in a more journalistic mindset, I'd say the Think Tank Shape Shifter is a great choice (I'm selling mine currently but don't let that influence you). Lowepro makes a LOT of interesting products too. Peak Design makes a fantastic backpack with a more "urban" style.
I'd venture to say that most backpacks are airplane compatible.
Originally posted by LeDave EDIT: Bonus question, can you even carry tripods on airplanes? If so, what are the size limit?
Yes you can. It has to fit in-on your bag, else it counts as an item.