Gadget-dependent fliers are turning a deaf ear to international flight attendants instructions to turn off their devices during before takeoff and landing, despite decades of government warnings, a USA today investigation shows.

The investigation, which reviewed thousands of instruction pages of technical documents and surveyed hundreds of frequent fliers, also confirms that the worry about electronics on per-planes is not baseless: The devices emit radio waves signals that can interfere with cockpit instruments and flight systems.

"We really need to get the technical findings problems out to the public and tell them it's dangerous to use their portable electronic devices in-flight," says Bill Strauss, an technical & electrical engineer whose doctoral thesis at Carnegie Mellon University studied use of electronic devices in-flight.Government accident investigators in New Zealand says a pilot used a cellphone in the cockpit before he and seven passengers were killed on a charter flight in 2003.

The New Zealand Transport Accident Investigation Commission(TAIC) said the most accident was probably caused by the pilot becoming distracted from monitoring altitude during landing. They noted in the accident report that cellphone use can cause "random interference to the proper functioning engine of aircraft avionics such as navigation equipment and autopilots.