Want to purchase a travel certificate for that special someone who loves to travel or perhaps send an annoying relative, spouse or roommate on a long trip somewhere far away? We’ve compiled a list of airlines and online agencies that offer gift certificates or gift cards. For the most part, you can simply purchase them online. The exceptions are US Air and Delta. You have to purchase those at the airport or over the phone. Since most cards can be ordered online they can be delivered via email or sent by mail to the recipient for a fee. The only certificates that we found with expiration dates were sold by Travelocity, Delta, and Continental. Those specific certificates must be used within a year. The rest do not expire (at least not until the airline selling them does). See below for other restrictions as these can vary from one company to another.