There are several programs which generate points that can be used to buy airfare. The amount of spending required to earn a flight will depend on the price of the ticket at the time you redeem. Similar programs award cash which you could, of course, use to purchase a ticket.

Here are some threads which discuss points (or cash back) programs that you may wish to consider:

http://www.flyertalk.com/forum/other...-prestige.html

http://www.flyertalk.com/forum/other...pital-one.html

http://www.flyertalk.com/forum/other...e-rewards.html

http://www.flyertalk.com/forum/other...lity-amex.html

http://www.flyertalk.com/forum/other...astercard.html

Note that the Travelocity Mastercard mentioned at the outset of this thread has been replaced by a Travelocity American Express, and the rewards program offered to new applicants is not as lucrative as the original version.