Investigators examining the fatal crash of an almost-new Lion Air jet, the first of the new Boeing 737 MAX model to suffer such a tragedy, will look at maintenance logs, the air traffic control exchanges with the pilots, the black box flight data, the cockpit voice recorder and the airline's safety history.

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The investigation of the fatal crash of a Lion Air jet that Boeing delivered less than three months ago — the first of the new 737 MAX model to suffer such a tragedy — will be painstaking, as the plane appears to have disintegrated on impact after a violent, high-speed plunge into the water Monday.

Yet initial clues as to what may have gone wrong on Flight JT610, leaving all 189 passengers and crew aboard presumed dead, may come relatively soon.

The crash site is in the relatively shallow coastal waters of Indonesia’s Java Sea, roughly 100 feet deep. The black-box flight data and cockpit voice recorders should be recovered quickly.

There is no information yet as to what caused the crash.

However, one immediate line of inquiry is into the handling of a technical fault on the airplane’s previous flight that, according to a flight log circulating online, indicated a problem with the jet’s air speed and altitude system.

Investigators will also study Boeing’s detailed records of how each part of this jet was built, particularly because it was completed during the chaotic production issues in Renton this summer.

Lion Air Chief Executive Edward Sirait said in a news conference that the fault reported on the jet’s previous flight, which he didn’t specify, had been fixed after instructions from Boeing before the plane took off again from Jakarta.

In an interview Monday, Jon Ostrower, aviation expert and editor of The Air Current, a digital aviation publication, said that according to standard practice after an airplane crash, “the first thing investigators look at is the maintenance logs and what was serviced in the flights preceding the accident.”

From those logs, the air traffic control exchanges with the pilots, the black-box data and the cockpit voice recorder, “I think we’re going to get an indication pretty quick” of the areas investigators will zoom in on, Ostrower said.

Indonesia’s transport-safety committee will lead the investigation. But because the plane was built in the United States, National Transportation Safety Board (NTSB) aviation-accident inspectors will assist with the inquiry, backed up by technical advisers from Boeing and U.S.-French engine maker CFM International, co-owned by General Electric and Safran.

According to international protocols, Boeing and U.S. safety regulators are required to stay mum on the details of such overseas investigations, deferring, in this case, to the Indonesian authorities.

Boeing’s 737 production troubles

The new MAX line of 737s first flew in flight tests in January 2016 and first entered service in May 2017 with Malindo Air, a Malaysian subsidiary of Lion Air.

At the end of September, Boeing had delivered 219 MAXs, with more than 4,500 others on firm order.

The jet that crashed, a MAX 8 model, flew for the first time in Renton on July 30 and was delivered to Lion Air two weeks later, on August 13.

Low-cost carrier Lion Air is one of Boeing’s most important 737 customers. As of the end of December, it had taken delivery of 196 of the airplanes with another 191 on firm order.

Since the beginning of 2017, Lion Air has taken delivery of 20 of the single-aisle 737s, including 13 MAXs.

Planes are normally delivered just four or five days after an initial check flight by Boeing pilots.

But this summer, a pileup of 737 production issues caused by late deliveries of fuselages and engines meant some planes sat for weeks on the edges of the airfield, where teams of mechanics worked constant overtime to complete the unfinished installation work.

The production issues caused chaos at the Renton plant, according to a veteran worker there.

Boeing brought in more than 600 employees from other Puget Sound facilities to help clear the logjam of airplanes, but these workers were inexperienced in the specifics of 737 assembly. The work was painstakingly slow.

Still, said the Renton veteran, even then quality inspectors didn’t cut corners before signing off planes for delivery.

“We’re definitely trying to make sure it’s safe,” he said, speaking as Boeing scrambled to increase deliveries in early September. “It’s not going to leave with any defects.”

Flight’s details

After delivery from Boeing, the jet that crashed Monday flew routinely for Lion Air for more than 10 weeks.

On Monday, it took off from Jakarta, the capital of Indonesia, at 6:21 a.m. local time, in good weather, bound for Pangkal Pinang.

The crew was cleared to climb but apparently encountered technical problems and reached a maximum altitude of 5,375 feet with erratic vertical speed values. The pilot radioed air traffic control and requested a return to Jakarta airport.

The vertical speed and altitude data before the crash, made available by Flightradar24, show an unusual drop in altitude about two minutes into the flight.

The vertical speed then goes up and down erratically. According to one pilot who offered his analysis of this data on the online pilot chat forum PPRune, “the pilots appear to be struggling to maintain a steady altitude” for the remaining 10 minutes of the flight.

In the last 20 seconds or so, the jet’s vertical speed increases sharply, then plunges, suggesting a stall and a loss of control.

Just 12 minutes after takeoff, the airplane entered a dive and crashed into the sea about 39 miles from the departure airport.

“The black boxes will be the definitive arbiter,” Ostrower said. The preliminary data indicates a deep vertical dive rather than any kind of belly landing.

Compared with a typical airliner’s descent rate of about 1,200 to 1,800 feet per minute, that data shows descent speeds quickly reaching 10,000 feet per minute and finally accelerating to 30,000 feet per minute, or 340 mph.

Pictures from Jakarta show floating debris from the plane broken into small pieces, along with personal items belonging to passengers such as cellphones and handbags.

“It would have been a very violent end to the flight,” Ostrower said.

The previous flight

Another data point for investigators is from the same jet’s flight the previous day. A flight and maintenance log from the jet’s one-hour-and-35 minute flight on Sunday has been posted online and appears genuine, though its provenance is unconfirmed.

This log lists a malfunction of the air speed and altitude indicators, in that they showed disagreement after takeoff. The flight deck would have three sets of such indicators, one for the pilot, one for the co-pilot and a third as a backup.

This seems to be the technical issue Sirait said was addressed and fixed before the fatal flight.

The log also lists, perhaps a result of this disagreement in the instruments, that the “Feel Diff Press” warning light was illuminating, which is a reference to a shift in the hydraulic pressure that determines the feel of the control column to the pilot.

On Sunday, the pilots flew on after these malfunctions and landed safely.

At this point, the issue that arose on the previous flight is no more than a clue to be examined. The pilot operating handbook would provide detailed checklists on how to deal with unreliable airspeed and altitude indications.

Ostrower said the 737 MAX’s airspeed data system, which draws from sensors called Pitot tubes, and its altitude data system are not significantly different from the same systems in Boeing’s previous 737 NG model and so are unlikely to be the source of some new problem.

Indonesia’s poor air-safety record

Another standard line of inquiry for investigators will be to study the maintenance practices of Lion Air Group, including Lion Air and sister airlines in Malaysia and Thailand.

The airline’s safety history is poor. Indeed, all of Indonesia’s airlines were blacklisted by European Union air-safety regulators and banned from entering EU airspace in 2007 because of concern over lack of regulatory oversight in Indonesia.

Lion Air was removed from the EU’s list of banned airlines in June 2016 after a safety audit from the International Air Transport Association (IATA).

A database compiled by aviation analytics firm FlightGlobal shows that before the JT610 disaster, Lion suffered 11 major accidents since 2002: the total loss of five aircraft, five accidents that resulted in major damage, and one minor loss.

In 2013, a Lion 737 with 108 people on board crashed just short of the runway and came down in the sea just over 20 yards from shore. Four passengers were seriously injured.

Among the contributing causes, according to the final accident report, were that the flight crew lost situational awareness and that the pilot in command called for a go-round when the airplane was too low to execute it successfully.

In 2002, another 737 crashed on takeoff when the pilots didn’t perform the takeoff check list correctly and attempted to get into the air with the flaps in the wrong position. Again, no one was killed but the plane was a write-off after it hit some trees beside the runway.

Indonesia’s recent safety record also includes the crash of an Indonesia AirAsia jet into the sea in 2014. All 162 people aboard that Airbus A320 died.

Ostrower said the EU blacklist had been a huge impediment to Indonesia’s aviation industry. With the Lion Air crash, the issue of the nation’s air safety standards “is almost certain to be reopened,” he said.

Correction: A previous version of this story said the pilot declared an emergency. When technical problems arose, the pilot did radio air traffic control and request a return to the airport but it’s unclear whether he declared an emergency.