Airlines have been ordered to replace Honeywell cockpit display units fitted to hundreds of Boeing jets which can be borked by wi-fi signals. The US air safety regulator said that tests had indicated that mobile phone and computer signals could cause the screens to go blank. These screens provide pilots with information about airspeed, altitude, heading and pitch and roll, and added that the fault could cause a crash.

The screens are not cheap and affected planes have several of them. Honeywell insists that it is all safe because the problem has not been experienced in-flight.

"We worked with Boeing and addressed any concerns in 2012 with new display hardware."

The problem was on "phase 3" display units which were susceptible to the same radio frequencies used to transmit wi-fi. The Federal Aviation Administration (FAA) said the screens could be disrupted by mobile satellite communications, cellular signals from phones, and air surveillance and weather radar. It believes more than 1,300 planes will need to be modified.

Plane maker Boeing said that it had recommended that carriers implement the changes back in 2012. More than 1,326 Boeing 737 and 777 jets still needed to make the change. A replacement programme would cost about $13.8m to implement and the changes were opposed by Virgin Australia, Air France, Ryanair and Honeywell.

Ryanair had complained that the demands imposed "a high, and unnecessary, financial burden on operators" and forcing all airlines to change the screens was "unnecessary." Therefore, if you are flying Ryanair it is always better to punch that guy with the iPhone sitting next to you. You can say you are saving the life of everyone on board while at the same time raising the standards of the universe.