This is not completely correct. From the GSA web site on FAQs about contract fares--Commercial airfares can be highly volatile, so an exception to the mandatory use requirement allows government travelers to take advantage of any low commercial fares offered by non-contract carriers, if the fares are also offered to the general public. Non-contract fares that are offered only to government travelers (sometimes called "DG" fares) are not included in this exception. Also, if the contract carrier for the particular market offers the lower fare, you still must use them, but at the lower fare. Travelers that use this exception would have to abide by the many restrictions that typically go along with lower commercial fares. Restrictions on discounted commercial fares usually include: non-refundability, change or cancellation fees, minimum or maximum stay requirements or extended calendar blackout periods.

CO no longer has any contract fares. They have the mentioned above DG fares, and those fares are the same as contract fares, but unlawful to use.

Another thing about gov't fares is that they MUST be purchased with a GSA cc, i.e. starts with 4486, at least the Visa. I know that AA will NOT issue a gov't ticket that is not purchased with a gov't cc.

I am a crazed mileage runner and it was easy the last two years when AA had 90% of the contract fares out of DFW, in addition to other pairs that I flew, e.g. JAX-LAX. They are down to about 75% out of DFW, and no longer have a lot of others. It was kind of nice when they flew into DAL, because that could be a backup.