I work for an accounting company and I am required to submit original airline receipts. When I don't use a ticket, the travel agent I'm required to use needs the paper ticket back to process a refund with any nonrefundable tickets receipts stamped "exchanged" and returned to me. I am then billed for any additional amount to cover a new ticket the nonrefundable didn't cover. My travel policy addresses any use of personal ff miles as "a gift to the company" and not reimburseable in any manner. Charging a company for an airline ticket and subsequently pocketing the money is criminal fraud. A couple of years ago a bunch of baseball umps were caught cashing in their union contracted first class tickets and getting coach tickets instead. Why not do the same with buying a discount airline fare and charging the full fare of the expensive airline? Why not drive and say you flew? All these are the same type of fraud. Not buying or using the least expensive travel within your company guidelines is unethical. Pocketing any gains from it is illegal.