Originally Posted by
Oaxaca
How likely you are to get a problem will depend on the desk/gate agent in front of you, but if they know the rules, they would be in the right to say your bag is non-compliant. Rules about baggage allowances carrying through the itinerary apply only to checked baggage, operating carrier rules apply for cabin baggage on every sector separately.
You were in the wrong if the bag exceeded AA permitted dimensions. I will admit I’ve got away with BA-compliant / AA non-compliant hand luggage several times on AA when connecting, though usually in domestic F, which seems to attract less attention. It’s one of the more irritating aspects of BA/AA connections for those of us who travel HBO wherever possible.
I am surprised to see that BA offers a more generous size to be honest. We've all seen (and many have remarked) on the size of US travellers' carry ons. It's because of this I would normally be thinking I would easily get away with it, but a few remarks here have made me think twice.