Read the text and answer the question:

Scientists possess hard \(and hard\-won\) evidence about what can bring down an airliner. Lightning. Wind shear. Pilot error. But as far as we know, not a single crash has been attributed to a Kindle. Or a MacBook Air. Or any of the couple hundred cell phones that invariably ride coach during a typical flight.
And yet we can recite by heart the announcement that precedes every takeoff and landing: "At this time, please turn off and stow all electronic devices, including laptops, cell phones, and MP3 players."
Why does the FAA put the kibosh on these seemingly harmless gizmos whenever a plane slips -- or renews -- the surly bonds of earth? One reason: emissions. "There are still unknowns about the radio signals that portable electronic devices \(PEDs\) and cell phones give off," say FAA documents. "These signals, especially in large quantities and emitted over a long time, may unintentionally affect aircraft communications, navigation, flight control and electronic equipment."

What do you think why electronic devices are not allowed on planes?