BERLIN (REUTERS) - European aviation safety authorities have issued an emergency directive for operators of the Airbus A350-900 long-haul aircraft to upload a software fix to prevent potential overheating of the hydraulic system and a risk of explosion.

Airbus has so far delivered more than 100 of the aircraft, which is flown by airlines including Lufthansa, Singapore Airlines, Cathay Pacific and Qatar Airways.

In the directive, the European Aviation Safety Agency (EASA) said that an overheat failure mode of the hydraulic engine-driven pump had been found - it can cause the temperature of the hydraulic fluid to rise fast.

If that is not noticed and corrected, it could, if combined with an inoperative fuel tank inerting system, lead to the fluid overheating uncontrollably, which could then, in turn, lead to the fuel-air mixture in the affected fuel tank igniting, EASA said.

Airbus said it had informed operators of the short-term software fix and was investigating whether further action was needed.