Interesting
article from IEEE Spectrum magazine in the US: researchers fitted a spectrum analyser into a carry-on bag and (with airline permission) flew around with it. Their conclusion:
More important, the data support a conclusion that continued use of portable RF-emitting devices such as cellphones will, in all likelihood, someday cause an accident by interfering with critical cockpit instruments such as GPS receivers. This much is certain: there exists a greater potential for problems than was previously believed.