"It was two hours into the flight -- this would have been classed as the 'cruise portion of the flight,'" he said. "You break down the flight into taxi, take-off, climb out and then cruise.
"So in that particular point of the flight, this is the safest part, nothing is supposed to go wrong. The aircraft is at altitude on auto-pilot, the pilots are making minor corrections and changes for height as the plane burns off fuel -- the plane will be going higher and higher -- so this is extremely serious that something happened at this point in the flight."
Greg Feith, a former investigator with the National Transportation Safety Board (NTSB) in the United States, suggested the pilots should have been able to report in, even if power on the aircraft had failed.
"The airplane by certification has to have battery back-up power -- they still have to be able to utilize certain flight instruments and communication tools to complete the flight safely. So you could lose all the generators, you could have both engines out, but the battery back-up -- which will only work for a certain time -- is intended for emergency situations."
