Sign up with T-Mobile, get free companion airfare

Up for a contract renewal for your mobile phone? Desperate for a cheap plane ticket? T-mobile might have your answer.

If you sign up for a two-year contract with the wireless provider, they’ll give you a free companion ticket to any seat that you buy. The offer is fairly flexible too: there are no blackout dates, tickets are good through 2010, you can earn frequent flyer miles and you can fly on any airline.

But there are also restrictions. The biggest one that I can discern is that you have to book your original ticket through a T-Mobile partner’s proprietary search engine — through which I hear you can’t get the “best” prices on all flights. As an example, one member at Flyertalk pointed out that a transcontinental flight was quoted between $600-$700, nearly twice that of which you could pay during a good fare sale.

Still, if you do your homework and find out that it’s economical to book the companion ticket, it may be worth looking into. You can check out T-Mobile’s promo page here while the Frequently Asked Questions page is here.