Cellular data plans are increasingly expensive, so bypassing the carrier could be much more economical for the consumer.

FORBES: The Future Of Wireless: The Case For Spectrum Sharing

Aircell's Gogo in-flight internet system, in use on several US carriers, offers only data connections now, but there have been reports of passengers bypassing blocks and using Gogo to conduct VOIP calls while in flight.

BBC: More flights allow mobile calls