[mbar84]

I'm trying to think how I would ideally set up such a system. The person traveling is in the best position to determine the most cost effective way to travel. Ideally you could somehow determine or negotiate ahead of time what travel expenses should be and then just pay that to the employee. Then they would just travel as they like and either pocket any savings they can find, fly cheaper if they value their time less than the saved money or pay extra if they value flying first class.

Good incentive structures are hard.

[shaftway]

The way Google did it was that you listed where you were going and what dates and they did some sort of magical formula to figure out your max allowable costs for the trip. They were always well above the minimum costs. For every $2 below the cap, you got $1 to be able to exceed the cap in the future. It ended up working out so about every 5 economy trips you could do one business class trip (depending on how economical you were). I felt like it aligned the incentives well.

[Doxin]

I'd set up some base rules. Semi-obvious stuff like no first class tickets or caviar dinners. And then I'd trust my employees to be adults.

Putting your trust in people is a great incentive structure.