The crash just after takeoff of an Indonesian airline jet carrying 189 people will confound investigators, because none of the familiar characteristics of an aviation disaster was present: the airplane, a Boeing 737 Max-8, was brand new, having entered service only in August; the Max-8 is the most advanced version of the 737; the airline involved, Lion Air, was recently upgraded to the highest safety level; and there was no weather involved.

The crash also came at a time when the safety record of airlines had reached an exceptional level: In 2017, not one passenger died on any commercial jet flight, anywhere in the world.

The only hint—which may or may not turn out to be related to this crash—is that on its previous flight the crew reported a technical fault that was, according to officials, fixed before the fatal flight. It is far too early to see any real significance in this, since it is quite common for small faults to be diagnosed by sophisticated monitoring equipment, and to alert maintenance crews in advance of landing.

Flight JT610 took off from the Indonesian capital of Jakarta, heading for the provincial capital of Pangkal Pinang, on the island of Bangka, but lost contact with air-traffic controllers after 13 minutes, and crashed into the Java Sea.

Once more investigators face an underwater search for a lost jet. But this will not present the same challenge presented by Malaysia Airlines Flight 370 that has still not been located since it disappeared in 2014. The Lion Air jet went down while not far from land on a busy air route. The Lion Air jet went down some nine miles from the coast in waters around 90 feet deep, which means that it should be swiftly accessible.

A similar disaster occurred in 2014, when AirAsia Flight 851 plunged into the Java Sea, killing 162 people. In that case it took seven days to locate the wreckage and bodies. Investigators discovered that a combination of a mechanical fault in the rudder of the Airbus A320 and a bungled response from the pilots led to the jet diving into the sea.

Because the Indonesian archipelago lacks a railroad and highway network, the nation has become unusually dependent on its airlines to provide commuter services between cities and the many islands, as was the case in this disaster.

Little more than a decade ago, Indonesian airlines had such a poor air safety record that they failed to meet the standards set by the European Union and were banned from European air space.

However, that picture has changed in recent years, and in July this year, all Indonesian airlines received clearance to operate in Europe. Garuda, one of these airlines and the only one with scheduled flights to Europe, has not had an accident in 10 years.

This year, Lion Air was one of three Indonesian airlines whose safety rating was upgraded to the highest level after meeting standards set by the International Civil Aviation Organization (ICAO).

The last major incident involving the airline was in 2013, when a Lion Air 737 landed short of the runway at Bali, ending up in shallow water, as a result of pilot error. There were no fatalities.

Last year, Indonesian air traffic controllers complained that Jakarta was handling more air traffic than the airport could safely handle. But that was not a factor in this case.

Indonesian air accident investigators have a good reputation. Their investigations meet the standards set by the ICAO and they publish, as required, detailed analysis of the causes of crashes. In this case, they will be looking at the very latest version of one of the world’s most popular airplanes. This crash should, by all normal criteria, never have happened.