Cockpit screens inside some older model Boeing 737 and 777 airplanes are vulnerable to interference from WiFi, mobile phones, and even signals outside the aircraft, such as weather radar, a 2014 safety bulletin from the Federal Aviation Administration (FAA) warned.
According to Bloomberg, the cockpit displays contain a glitch that makes them susceptible to going blank during flight. If this happens, critical flight data including airspeed, altitude, and navigation could vanish and “result in loss of airplane control at an altitude insufficient for recovery,” the FAA said in its airworthiness directive.
Interference from cell phones can pose a threat to the Boeing planes even when the phones are switched to airplane mode, Bloomberg reports. That’s because airplane mode still allows the transmission of WiFi signals, which are transmitted at higher power from a cell phone because they must reach a transmission tower instead of a local antenna or router.
Boeing contracted Honeywell International Inc. to manufacture the cockpit screens for about 1,700 737 and 777-model airplanes worldwide. The 737s affected by the display problem are Boeing’s Next Generation models, often called the 737NG. These planes are the predecessor of the Boeing Max model, which was involved in the crashes of Lion Air flight 610 and Ethiopian Air flight 302, which killed 346 people combined. Those crashes have exposed serious deficiencies within Boeing aircraft and the FAA’s approval process.
According to Bloomberg, Rockwell Collins manufactured the cockpit displays in Boeing’s Max airplanes.
Most of the aircraft affected by the at-risk displays – about 1,300 – are registered in the U.S. Delta and Southwest have upgraded the systems in all their affected Boeing jets. American Airlines and United Airlines are operating jets that have not undergone the FAA mandated repairs. The airlines have until November of this year to comply with the directive.
After discussing the matter with Honeywell, Bloomberg estimates that the problem still affects about 1,700 units in more than 280 planes. Each of the Boeing planes has six of the cockpit displays.
The Irish discount airline Ryanair told the FAA in 2014 that 707 of the affected Honeywell cockpit screens were installed in its fleet of Boeings. The airline said at the time it wouldn’t replace all the units because of the “high and unnecessary financial burden” overhauling the systems would place on it. The airline said it inspected and upgraded the display units and replaced those with issues.