Be careful covering an expense. Unless you enjoy chasing after money, don't float any operator a loan for hotels, gas for the plane, rental car, airline ticket or anything, really.
If they can't afford to just cover it and be done with it, how will they afford your bill when it comes in? And if it is just down to not "trusting" you with a company card, then they should find someone else that they do trust.
I don't float a loan for operating an airplane and if I'm not paid on time, the plane doesn't move. Period. I've had to chase after money too many times in the past.
-mini