Never-ending problems of the Boeing 737 MAX have already become a one-year saga of twists and turns. This time Boeing has discovered ‘foreign object debris’ in the fuel tanks of grounded MAX aircraft, Leeham News reported.

Following the discovery, Boeing has ordered inspections of its entire grounded 737 MAX fleet, consisting of over 400 planes.

According to Leeham News, it could take up to three days to examine each aircraft, as “fuel must be drained and vapors dissipated before the fuel tanks can be opened”.

Taking this into account, the checks should not delay the recertification process.