As you probably know, one of the new features in the iPhone 3G is the built-in GPS radio, which lets you pinpoint your location for hipster-loving social networking apps like twitter and loopt. In Steve Job’s WWDC keynote, he showed off the GPS functionality with a video of the Maps application tracking a car as it drove down Lombard Street in San Francisco. The blinking blue dot followed the car as to passed each block, updating at a short enough intervals to move fluidly. While that’s cool and practical, we wanted to push the iPhone’s GPS to its limits. And the best way we could think of to stress test vehicle tracking was to try it on a moving airplane.

 We decided to run the Maps application and track our location during an hour-long flight from San Francisco to Los Angeles. At 10,000 feet in the air, we knew we wouldn’t have any cellular reception, so the phone couldn’t download terrain or map data from Google Maps. Still, we were hoping that we’d get to at least see a blue dot zipping along a grey background. And in case you were wondering, our in-flight magazine listed GPS receivers as acceptable devices to use once the plane has reached a its cruising altitude.

Unfortunately, the Maps app wasn’t able to detect or utilize GPS information during the flight, and just displayed a standard “no data network found” error message.

On our return trip to San Francisco, however, we thought it would be smarter to start up the Maps application before the plane had taken off, so we could buffer all the surrounding map data before getting in the air. As the plane started turning and strolling to the runway, we saw that the live tracking was working! We were only a couple meters above the ground and moving an estimated 30-40 miles per hour, but this was very exciting (because we're tech geeks)

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As the plane sped up to reach takeoff speed (about 150mph for a Boeing 737), the blue tracking dot started only updating every second, skipping along on the screen. At one point, the blip even indicated that we were on a nearby highway adjacent to the airport. The dot kept locked on and updating through the actual takeoff – huge success! A second after that, our reception quality shrank from five bars to two. And shortly after that, the map automatically zoomed out and removed the pinpoint tracker, resorting back to the cellphone triangulation tracking. At that point, we had already been off the ground for a good 10 seconds, so the plane was probably moving faster than 200mph.

Read on for screencaps of the GPS in action during takeoff!