Divers scoured the Java Sea on Tuesday looking for clues that could explain why a brand new airliner fell out of the sky just moments after takeoff, killing all 189 people on board. Before Lion Air Flight 610 lost contact on Monday, the plane displayed erratic changes in its speed, altitude and direction, causing experts to speculate that a problem with the aircraft’s instruments used to calculate airspeed and altitude may have contributed to the crash. Those indicators, or pitot tubes, have been implicated in previous aviation disasters, but experts said that determining the cause of the crash would ultimately require the recovery of the plane’s flight data recorders, the so-called black boxes.Flight 610 departed Jakarta, Indonesia, on Monday at 6:20 a.m. Soon after takeoff the plane reached an altitude of 2,100 feet before falling precipitously to around 1,475 feet, according to satellite data transmitted from the airplane and collated by the aviation website Flightradar24. Moments later, the plane climbed to altitudes varying between 4,500 and 5,350 feet. The data then shows a steep decline, until contact was lost at 6:32 a.m.In a normal flight, the lines in the chart above representing speed and altitude would level off into a smooth plateau, but on Monday’s flight they fluctuate erratically. “The erratic flight path makes us suspect a problem with the pitot-static system,” Gerry Soejatman, an Indonesian aviation expert, told The New York Times. Pitot tubes on an Airbus A380 airplane. The plane involved in Monday’s crash was a Boeing, but the tubes are found on most commercial aircraft. CreditPascal Rossignol/ReutersWhat’s a Pitot Tube? Pitot tubes, slender perforated tubes on the wings or fuselage of an aircraft, are used to determine airspeed, a measurement vital to controlling the plane: Too slow and the aircraft can stall, too fast and it can break apart. Each tube has two holes in it: a hole in the front into which the airstream flows and a hole in the side. By measuring the differences in the “stagnation pressure” at the front and the “static pressure” at the side, one can calculate airspeed. The tube is named for Henri Pitot, an 18th-century French scientist who invented the tool to measure the speed of flowing rivers. Malfunctioning pitot tubes contributed to the infamous disappearance of Air France Flight 447 over the Atlantic in 2009. Investigators attributed that crash to ice crystals forming over the tube’s intake, leading to erroneous measurements and the flight crew reacting incorrectly. Experts cautioned that it was still too early to determine the cause of the accident, and that often equipment malfunctions and human error both contribute to crashes. The PlaneMonday’s crash was the first disaster involving a Boeing 737 Max 8, an updated version of the best-selling Boeing 737.The Max 8 has been in commercial operation for only a year. The plane in this week’s disaster was first put into use in August and had logged just 800 hours in the air, according to Indonesian officials. Edward Sirait, Lion Air’s president director, said the plane had experienced an unspecified technical problem during a flight the day before. He said the issue had been resolved “according to procedure.”Experts examining the data from that flight said there appeared to be a similar problem with measuring the plane’s airspeed. A Checkered HistoryIndonesia’s aviation industry has long been dogged by accidents and accusations of malfeasance. The United States and the European Union banned Indonesian carriers for years, citing a lengthy record of crashes. The United States lifted its ban in 2016 after nearly a decade, but it was only in June that the European Union began letting Indonesian airlines fly there. Among recent notable accidents was the crash of a 2014 AirAsia flight to Singapore, in which 162 people were killed, and a 2015 Trigana Air crash in Papua, Indonesia, in which 54 people were killed. Twenty-five people were killed in 2004 in the last fatal Lion Air crash. Luckily, no one was killed in 2013 when a Lion Air jet missed the runway and crashed into the sea in Bali.