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It might be that the main issue isn't the safety of the plane, but of the passengers on the plane. If you'll note, many planes have wireless internet - but you're not allowed to use it during takeoff and landing. During those two periods, the pilot and copilot need to focus on doing their jobs, but for a good part of the flight, it's not as dangerous or stressful. During takeoff and landing, the last thing the airline staff want to be dealing with is people talking on their cellphones or blasting music on their iphones. but during the rest of the flight, it's a little more relaxed.