I am a pilot for an airline and while I don't believe a Kindle or any other electronic device would interfere with the airplanes electronics, the Federal (FCC+FAA) Law says that NO electronic devices may be operated below 10,000' unless advised by your crew. My airline allows the use of cell phones after landing for example. So I would have to enforce the Federal Laws as the captain or else bad things could happen to me, by the Feds.