The blaze, which started as the Egyptair jet with 291 passengers on board prepared to depart for Jeddah, caused extensive damage to the cockpit and fuselage.
Passengers and crew were evacuated safely but investigators pinpointed a problem with the cockpit hose used to provide oxygen for the crew in the event of decompression.
It is believed a short circuit caused the pipes to ignite, causing extensive damage to the plane.
“In simple terms, this fault can cause a blowtorch type fire that will melt aluminium in a matter of seconds,” said James Healy-Pratt, an aviation lawyer and qualified pilot.
The Federal Aviation Authority in Washington and the European Aviation Safety Agency issued directives to airlines under their control.
It required the oxygen hoses on the bulk of the 777 fleet to be replaced with an alternative which did not conduct electricity.
The FAA estimated carrying out the work would cost $2,596 (£1,573) per aircraft.
It is unclear whether similar instructions were issued by regulators in Malaysia.
Boeing said it would be inappropriate to discuss what modifications were made to the global 777 fleet or what advice it sent to airlines in the aftermath of the Cairo fire.
There is growing belief that an on-board fire could explain what happened to the plane, rather than an act of terrorism.
“We believe that in due course, the crew will be regarded as heroes rather than villains, and we sincerely hope the Black Boxes will contain the data to back that up, and to prevent further needless loss of life,” Mr Healy-Pratt added.
Chris Goodfellow, a Canadian qualified pilot and aviation blogger, also voiced support for the on-board fire theory.