This is a tough one -- I try to schedule my calls around my travel schedule so this doesn't happen but it doesn't always work like that, especially if you are about to step on a long flight (especially TCON/TATL/TPAC). If work is paying for me to travel somewhere there's an expectation that I'm available during the course of my travels.
Of course that doesn't mean one should be divulging confidential information or screaming loudly. I try to find the quiet corners but in some SCs it's just not possible (RDU is particularly challenging during busy times because the cubicle area is still pretty open and the rest of the SC is pretty compact -- and I often need to hop on a call at the end of the day when I've timed to take the post-work flight but need to get to the airport with time to park and make it through security).