Australian airline Qantas has said it will continue to keep its fleet of six Airbus A380 planes grounded while further safety checks are carried out.
Last week the engine on a Qantas A380 exploded in mid-air, forcing an emergency landing in Singapore.
Qantas had initially expected the checks to be completed by Thursday.
Meanwhile, Europe's air safety regulator ordered airlines to carry out more tests of A380s using the same type of Rolls-Royce engine as Qantas.
The European Aviation Safety Authority said a fire caused by an oil leak was the most likely cause of the engine failure in the Qantas jet last Thursday.
Qantas said it was updating its international flight schedule to take account of the grounded A380s. The plane is the world's largest passenger aircraft.
"Our A380 aircraft will still be grounded for the next 48 hours," a Qantas spokeswoman told Reuters news agency.
"At this stage we have no firm update when the aircraft will be in the air."
Qantas earlier said it found "oil where oil shouldn't be" on three engines of its A380 fleet.
Chief executive Alan Joyce said this was unusual given that they were only two years old.
Not all A380 aircraft use Rolls-Royce Trent 900 engines. These have been chosen by Lufthansa and Singapore Airlines, as well as by Qantas.
Singapore Airlines has announced it will change the engines on three of its 11 A380s, replacing them with new versions of the same model.