If Cell Phones were such a critical thing to not have turned on do you not think the crew would walk the isles with detectors prior to takeoff and if it was such a critical issue. Don't you think you would have to check in your cell phone and have is locked down for the flight. Estimates were last year that some absurdly high number of flights left the ground in the U.S with one or more cell phones still turned on many actually just silenced.
Phil
Mythbusters will be testing the myth about cell phones interfering with plane navigation and control.
"Episode 49: Cell Phones on Planes
So supposedly, if you fill a normal raft with helium, you can fly. Let's see it ? get ready for the biggest Mythbusters' build ever. Meanwhile, Tory and Kari tackle a conspiracy theory familiar to many frequent fliers. Can your cell phone interfere with a plane's instruments?
premiere: March 15, 2006"
http://dsc.discovery.com/fansites/mythbusters/episode/episode.html?clik=fanmain_leftnav

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