Have you ever, while taking off or landing in an airliner, felt any great confidence that everyone on the flight had actually turned off their cell phones, as instructed? No, right? And have you ever been on an airliner that crashed? I'm guessing not. Doesn't that make you wonder how dangerous it really is for people to leave their cell phones on during takeoff and landing?
And it's not as if your flights are the only data points. Every day, thousands of airliners containing active cell phones take off and land--and nothing bad ever happens.
Of course, this argument against what may be the most gratuitously annoying airport security measure is conjectural, since I've never actually surveyed my fellow passengers to see how many had their cell phones on. But, happily, two psychologists have now taken the conjecture out of the argument. I give you Daniel Simons and Christopher Chabris, writing in the Wall Street Journal's Weekend Review*:
[W]e recently conducted an online survey of 492 American adults who have flown in the past year. In this sample, 40% said they did not turn their phones off completely during takeoff and landing on their most recent flight; more than 7% left their phones on, with the Wi-Fi and cellular communications functions active. And 2% pulled a full Baldwin, actively using their phones when they weren't supposed to.
Consider what these numbers imply. The odds that all 78 of the passengers who travel on an average-size U.S. domestic flight have properly turned off their phones are infinitesimal: less than one in 100 quadrillion, by our rough calculation. If personal electronics are really as dangerous as the FAA rules suggest, navigation and communication would be disrupted every day on domestic flights. But we don't see that.
As Simons and Chabris note, there's never been any good evidence that cell phones or other electronic devices disrupt navigational equipment or communications between pilot and ground. In fact, attempts to create these effects have failed.