In my company any time spent traveling is on the clock. You don't charge for time in the hotel room, but time at the airport/in a plane/in the taxi all counts. The expenses people will cross reference your timecard to make sure you did it right too.

It's kind of annoying actually, because it means feeling guilty if you aren't working while on the plane, but at the same time I can't work because the seats are too close together and the guy ahead of me has reclined all the way so I can't even open my laptop.