Originally Posted by docbert

Some airlines used to explicitly prohibit any radio transmitters or receivers. In fact, rather stupidly, United's website actually states even today that "Radio receivers and transmitters" can't be used during flight. The same page also states that laptops and seat charging ports can't be used below 10,000 feet which is outdated, not to mention that they have Gate-to-gate wifi which obviously uses "Radio receivers and transmitters"... I do recall at least one airline I've flown that explicitly listed GPSes in their 'Not Allowed' to be used list, but I don't remember who it was (probably an Asian carrier I suspect). United Airlines had them listed in their in-flight magazine as being allowed for several years, but I think that's gone now.

For some time it was actually illegal to use certain radio receivers on US airlines (eg, this ruling), but that was very far in the past...