Japan's All Nippon Airways will delay retiring four aircraft to help maintain services already hit by the grounding of its entire fleet of troubled 787 Dreamliners, Kyodo News reported on Saturday.
International regulators grounded all Boeing Dreamliner jets in January after a battery on a Japan Airlines 787 caught fire and forced an ANA flight to make an emergency landing.
ANA had initially planned to retire a Boeing 747 jumbo jet in April and three other smaller aircraft -- including the Airbus A320 -- between March and May, but their retirements will be postponed to June or later, Kyodo said.
The aircraft are currently being used for domestic flights amid the cancellation of domestic and international services while the Dreamliners remain grounded, it said.
The firm is also seeking to introduce three Boeing 777 jets earlier than planned to minimise the impact of the no-fly order, it added.
Immediate confirmation of the report from ANA was not available.
The carrier said late in February that it was cancelling 1,714 flights in April and May, a period that includes Japan's busy Golden Week holidays, taking the total affected to more than 3,600 since January.
Boeing said last week that the 50 planes grounded around the world since two lithium-ion battery malfunctions sparked a global no-fly order in mid-January would undergo fixes to their systems and be operational again soon.
A Boeing 787 took off from Seattle on a test flight on Monday to see if a redesigned battery system works properly while the plane is in the air.
The test flight is an important step in Boeing's plan to convince safety regulators to allow airlines to resume using the plane, which the company calls the Dreamliner.
Boeing filed a flight plan shortly before the plane took off from Paine Field near Seattle on Monday (Tuesday morning AEDT).
Boeing added insulation around battery cells and a steel casing on the outside to prevent fires. Company officials have said they might never know the cause of the smouldering batteries, but they hope to get the planes back in the air within weeks, not months.
The National Transportation Safety Board and Japanese authorities are investigating the incidents.
The NTSB plans to hold a forum next month in Washington on the use of lithium-ion batteries in transportation. The agency said on Monday the event from April 11-12 will focus on design and performance of the batteries and regulation of their manufacturing and use.
Monday's test flight was expected to last about two hours. Boeing used a 787 that it built for LOT Polish Airlines.
Boeing spokesman Marc Birtel said the plane's crew would test landing gear, electrical and backup systems, and ''demonstrate that the new battery system performs as intended during flight conditions''.
Birtel said once the flight is done, Boeing will analyse data from it and prepare to seek certification.