Travel backpacks and bags
Osprey Fairview 70
Osprey Farpoint Trek 55
Travel backpacks sport a couple of travel-specific additions to back country packs: they tend to have detachable daypacks and they often have a panel that can be used for hiding the carrying system from those ever-so-cruel conveyor belts at airports.
Some smaller travel bags have been made specifically to fit into the box that some airlines use to limit hand baggage size.