Little more than six months after Boeing's 737 Max was cleared to fly again by US regulators, the aircraft finds itself under intense scrutiny once again.The discovery of a potential electrical problem last month led to the renewed grounding of more than 100 aeroplanes, belonging to 24 airlines around the world.
Boeing and the US regulator, the Federal Aviation Administration say they are working closely to address the issue.
Those critics include a high profile whistle-blower, Ed Pierson, who has already sought to link allegedly poor production standards at the 737 factory with electrical defects on the crashed planes, which he claims may have been implicated in both accidents.
The fault was traced to poor electrical bonding, where panel assemblies that were also intended to conduct electricity and form part of a connection with the frame of the aircraft were not doing so effectively.
The actual modifications required are expected to be relatively simple and are only expected to cost about $2,250 (£1,600) per aircraft.