Unfortunately, "airline carry-on approved" can vary in reality according to the type of plane and flight. I avoid using my larger Lowepro Computrekker for this reason, though it is "carry-on approved."
All valuable and necessary equipment stays with me on the plane. I use a Think Tank Airport Ultralight---only good as a daypack. (You can pack a heavier duty pack in your check in luggage) Phase body and P65+, lenses, Cube, etc. go in the Airport Ultralight. As long as you do not overpack the Ultralight, it will fit into a Pelican 1510. If you get "tagged" at the gate, pull out the Ultralight pack, and let the airline gate check an empty Pelican.
Tripod legs in a soft case go into a hard shell suitcase with clothes, etc. Other than the tripod legs, I figure I can pretty much buy new clothes or whatever the airline loses in the worst case scenario.
Really screwy with the airlines. They will charge you $ if you go over say 50lbs on check-in luggage. So, pack in one suitcase to save space---but hit 52 lbs, and you get nailed. But if you divide up the load between two large suitcases---you won't pay the surcharge, even though the two cases take up twice as much space, and actually more weight because of the additional case.
I've also had the airline check-in staff have me remove items to "make-weight" and then advise me to put the items back into the suitcase right before you drop the case off to Homeland Security to scan and receive.... Boy, that makes sense....