The US authorities have instructed airlines to inspect some 2,000 Boeing aircraft that have been grounded due to the corona crisis.
These are aircraft that have not flown for seven days or more.
The FAA aviation authority wants to be checked for corrosion of certain parts of the Boeing 737 NG and Classic.
This could lead to engine failure. Reports of such problems have been reported repeatedly in recent times.
Corrosion could occur more often if aircraft are not used for a long time.
This is now much more common than usual because the demand for air travel has decreased considerably due to the pandemic.
Aircraft builder Boeing says it will support airlines that face problems.