Older Airbus A380 operators are set to be ordered to check for cracking in the region of the outer rear wing spar.
The European Union Aviation Safety Agency has disclosed that cracks have been discovered in this area, notably on top and bottom flanges between ribs 33 and 49.
Both wings are potentially affected, says EASA in a proposed directive, adding that the situation could reduce the wings' structural integrity.
Airbus is planning to issue a service bulletin containing detailed inspection instructions, requiring phased-array ultrasonic testing for the wing box.
EASA says the directive would be limited to the 25 oldest wing sets on the A380 fleet, although it could subsequently expand to cover additional aircraft.
Nine of the 25 aircraft were delivered to Emirates, another six to Qantas, seven to Singapore Airlines – although some have since been withdrawn, with one going to Hi Fly – plus two to Air France and one to Lufthansa.
EASA says the detailed inspections should be carried out within 180 months of the wing-box assembly date or 147 months since Airbus's date of manufacture, and be repeated every 36 months.
Operators detecting any cracks are being instructed to contact Airbus before the next flight for repair instructions.