Wi-Fi provider Boingo will offer Apple iPhone and iPod Touch owners the opportunity to enjoy 15 minutes of free Wi-Fi service at 28 airports located in the United States, United Kingdom and Canada.

What's the catch? Users interested in the service will have to watch 15 seconds of video advertisements before having access to the Internet uninterrupted for 15 minutes.

The free service is available to air travelers in the United States at Baltimore-Washington International, LaGuardia and Kennedy airports in New York City, Houston Hobby, Metro/Wayne County Airport in Detroit, and Midway and O'Hare airports in Chicago, among others nationwide. Users in the United Kingdom can find the service at London Heathrow, Edinburgh, Gatwick, and Stansted.

Boingo plans to make the service available to Sony Ericsson, Nokia and Microsoft Windows Mobile users in the future, though no official launch date has been announced. Last August, Boingo rolled out a free trial for 13 airports that lasted the entire month. Since that time, Boingo has apparently garnered enough interest to feel confident enough to offer such a service on a permanent basis.

The company typically charges users $21.95 per month for North American access and $39 for a Global account to have access to more than 100,000 Wi-Fi hotspots using only one username and password.

Many airports have Wi-Fi access available to users waiting to board their flights, but the fees are high enough where non-business people will likely shy away from using it. Typical pricing starts at $6.95 for daily Internet use, with prices as high as $10.95 or more.