Also, the company frequently hands out positive space tickets as a reward or incentive. I think I have 12 or 16. They do expire (eventually) and you still have to pay taxes and fees for the tickets. I've never tried to use mine, but I've heard that fees can run $70 - $100 per person per flight segment.
The biggest problem with using the tickets is space availability. If you go to our company travel link, it will show the number of authorized positive space seats for any given flight. Some are "0" (zero). Expect to travel at some odd time of the day, or the during the middle of the week.