Gadgets are tested by monitoring the number of volts per meter coming off a device. The F.A.A. requires that before a plane can be approved as safe, it must be able to withstand up to 100 volts per meter of electrical interference.

When EMT Labs put an Amazon Kindle through a number of tests, the company consistently found that this e-reader emitted less than 30 microvolts per meter when in use. That’s only 0.00003 of a volt.

“The power coming off a Kindle is completely minuscule and can’t do anything to interfere with a plane,” said Jay Gandhi, chief executive of EMT Labs, after going over the results of the test. “It’s so low that it just isn’t sending out any real interference.”

But one Kindle isn’t sending out a lot of electrical emissions. But surely a plane’s cabin with dozens or even hundreds will? That’s what both the F.A.A. and American Airlines asserted when I asked why pilots in the cockpit could use iPads, but the people back in coach could not. Yet that’s not right either.

“Electromagnetic energy doesn’t add up like that. Five Kindles will not put off five times the energy that one Kindle would,” explained Kevin Bothmann, EMT Labs testing manager. “If it added up like that, people wouldn’t be able to go into offices, where there are dozens of computers, without wearing protective gear.”