Certain Airbus A340-500 and -600 operators are set to be ordered to replace centre landing-gear axles on the type after concerns that a batch underwent improper maintenance treatment.
The European Union Aviation Safety Agency says corrosion was discovered on an axle in the wheel interface area during an overhaul.
It states that the most likely cause is "non-systematic stripping of chrome" during the overhaul and "insufficient" non-destructive testing.
EASA says it has identified a specific batch of affected parts which has been subjected to the "inappropriate" process.
The aircraft involved comprise 13 A340s with serial numbers between 606 and 761.
Manufacturer Safran has drawn up replacement instructions. The regulator says the condition could potentially result in axle failure on the type.