JAKARTA (NYTIMES) - The ageing plane flew during a heavy storm in a country with a long history of flight disasters. It had also been out of service for nine months.
According to Indonesia's Ministry of Transportation, Sriwijaya Air Flight 182, which plunged into the Java Sea on Saturday afternoon, killing all 62 passengers and crew members on board, had been in a hangar for most of last year after the coronavirus pandemic wiped out much of commercial flight.
The effect such a hiatus may have had on the 26-year-old Boeing 737-500 is still unclear, but experts have warned that the continuing collapse of air travel could pose potential safety risks from mothballed planes.
"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 period of dormancy creates extra burdens for inspections and maintenance to repair parts that may have deteriorated. In addition, pilots who may not have been flying actively during the downturn need time to get back up to speed, Ritchie said.
"All of these aircraft have to be brought slowly back into service," he added. "The same can be said about pilots." For pilots, flight simulator training is a key way to maintain proficiency after lost flying time.
Like most commercial airlines, Sriwijaya Air was forced to scale back operations in the pandemic. At one point it was down to operating just five of its 18 planes. The Boeing 737-500 that crashed was put in a hangar on March 23 and did not operate again until the end of the year, according to the Ministry of Transportation.
The airlines' pilots also faced long periods on the ground. Captain Afwan, the pilot in command of Sriwijaya Air Flight 182, spent much of his time last year in flight simulator sessions to maintain his skills.
The Ministry of Transportation said it inspected the plane on Dec 14 and issued a new certificate of airworthiness on Dec 17.
After the plane resumed service last month, it was flown from storage in Surabaya to Jakarta, the capital, on Dec 19. It resumed passenger service the next day, according to data from the tracking site Flightradar24.
The plane had conducted 132 flights since it left storage, said Ian Petchenik, a Flightradar24 spokesperson.
"We can't speak to whether or not storage may have been a factor in the crash, but investigators will certainly be looking at all possible scenarios," Petchenik said in an email.
"The readout of the flight data recorder will hopefully prove helpful in determining the cause."
Navy divers recovered the plane's flight data recorder on Tuesday, one of two so-called black boxes investigators will use to find out what happened.
Officials believe the location of the second black box - a cockpit voice recorder - has been pinpointed about 50 feet (15m) away from the flight data recorder that was recovered on Tuesday.
Treacherous weather conditions and wreckage scattered in mud roughly 75 feet (22m) underwater made finding the devices difficult. The first recorder was recovered by divers moving large pieces of debris and digging by hand in the mud, said Adm. Yudo Margono, chief of staff of the Indonesian navy.
The pattern of debris suggested the plane hit the water relatively intact. Indonesia's National Transportation Safety Committee said Tuesday that it did not explode before crashing.
The search between the small islands of Lancang and Laki was suspended on Wednesday as waves reached a height of 8 feet (2.4m).
Sriwijaya Air had undergone an independent audit last March that assessed licences, operation manuals, spare parts, safety- and quality-system management, crew training and aircraft supervision, said Jefferson Irwin Jauwena, Sriwijaya Air's chief executive.
The audit was carried out through the Basic Aviation Risk Standard program run by the Flight Safety Foundation, a nonprofit based in Alexandria, Virginia.
The National Transportation Safety Board said it was sending a team of four investigators from the United States to help look into the crash. The team will be joined by experts from the Federal Aviation Administration, General Electric and Boeing, the board said.
Indonesia waived its coronavirus travel restrictions for the investigators.
Sriwijaya Air Flight 182 crashed just four minutes after takeoff from Jakarta, plunging more than 10,000 feet in under a minute. Officials have identified the remains of six victims so far.
The plane was bound for the city of Pontianak, on the island of Borneo. The quick trip was scheduled to last a little over 90 minutes. The plane had completed four other flights earlier in the day.