I believe the published dimensions by Osprey fit BA but not TAP. I say published because not all luggage manufactures measure handles and exterior pockets as a part of the listed dimensions so it is a good idea to measure your bag empty and packed. Since the Osprey is a soft sided bag it is easy to over pack it. If I remember correctly there is an arch in the Osprey bags that could make a difference because the airline sizers are fixed measurements.

I like to measure my luggage on a table. That gives you a solid flat surface to measure from.

The key question is will you get checked and I can't tell you. What I can say is after you pack your bag and it is not it line with the airlines rules be prepared for it to be checked.

I live near a regional airport and after packing my carry on I put my bag in the sizer of the airline I am going to fly on.

Shak