Florida Keys vacationers can get a free companion airfare certificate, good for future passage on five legacy U.S. airlines when they stay in a room for two or more nights at participating Florida Keys accommodations.

The promotion is valid through March 31, 2010.

Keys properties included in the program are listed here.

While area tourism officials hope visitors will utilize the companion fare to return to the Florida Keys, the certificates can be used for travel anywhere within the continental United States.

The certificates must be used within a year of being awarded.

As per Federal Aviation Administration security regulations, airlines collect applicable service fees and taxes directly from certificate holders.

The program is administered by Airline Promotions Inc.