Officials investigating last Saturday's Boeing airliner crash in Indonesia are understood to be probing a possible link to the plane's prolonged grounding during last year's Covid-19 lockdowns.
The 27-year-old Boeing 737-500, which crashed into the sea off Jakarta with 62 people on board, spent nearly nine months out of service last year because of reduced flight timetables caused by the pandemic.
While officials conducting the inquiry have not yet commented on the cause of the crash, experts are now speculating that it may be due to technical faults caused by the plane's lack of regular use.
The exact cause of the crash is still unknown, however. On Tuesday, Indonesian navy divers recovered the "black box" flight data recorder from the plane, which abruptly plunged nearly 10,000 feet just minutes after take-off.
Officials believe they have also located the second black box — a cockpit voice recorder — about 50 feet away from the flight data recorder.
Indonesian officials have said that the plane passed safety inspection checks on December 2 - including for engine corrosion - and was declared airworthy on December 14.
Sriwijaya Air, the local airline that operated the plane, also has a good record of service. It is not unusual for 27-year-old aircraft to be in service in the region, nor for 132 flights to be made within weeks of being pressed back into service.
"This is pretty standard for this airline and this part of the world," Ian Petchenik, a Flightradar24 spokesman, told the Wall Street Journal. "Because aircraft are the main source of connectivity, there are a lot of short routes with high frequencies."
But he said that problems caused by the airliner's prolonged "storage" period would be among the scenarios that the flight crash investigators would be looking into.
More than 3600 rescue personnel, plus 13 helicopters and 54 large ships have been scouring the area where the airline sank on Saturday afternoon, in water 75 feet deep. The search has been hampered by bad weather, but large numbers of bodies have already been found.
The chairman of Indonesia's National Transportation Safety Committee, Soerjanto Tjahjono, has ruled out a possible mid-air breakup after seeing the condition of the wreckage found by searchers. He said the jet was intact until it struck the water, concentrating the debris field.
The disaster has re-ignited concerns about airline safety in Indonesian airlines, which were banned from operating in the EU between 2007 and 2018.
"There's a major problem starting to raise its head in terms of restoring these aircraft because while out of service for nine or 10 months, they need to be kept operating, otherwise they deteriorate," said Hugh Ritchie, chief executive of Aviation Analysts International, an Australian air safety consulting firm.
The Indonesian plane did not fly between March 23 and December 19 last year, and was then used 132 times after it resumed operating, according to aviation data provider Flightradar24.
John Goglia, a former member of the US National Transportation Safety Board, said that long-grounded jets required up to a fortnight's worth of enhanced maintenance checks to two weeks to ensure that electronic, hydraulic and fuel systems had not deteriorated.
Goglia said that his initial thought on learning about the Indonesian plane's long grounding "was if they did the proper due diligence ... because sometimes that stuff doesn't show up for a little while".
Ritchie added that it was important also to ensure that pilots too needed to ease themselves carefully "back into service" after prolonged periods of inactivity due to the Covid lockdown.
The pilot in command of Saturday's crashed flight had spent much of his time last year in flight simulator sessions to maintain his skills.