An Indonesian passenger plane that crashed into the Java Sea on October 29 experienced problems with its airspeed indicators on its last four flights, data from one of the flight recorders retrieved from the aircraft has revealed. All 189 people on board the Lion Air flight JT 610, flying from Denpasar to Jakarta, were killed.

“When we opened the black box, yes indeed the technical problem was the airspeed or the speed of the plane,” head of Indonesia’s National Transportation Safety Committee Soerjanto Tjahjono said, according to The Guardian. “Data from the black box showed that the two flights before Denpasar-Jakarta also experienced the same problem. In the black box, there were four flights that experienced problems with the airspeed indicator.”

Airspeed is measured using pitot tubes, sensors which record pressure on the wing or front surface of the aircraft. The pitot tubes can become blocked for various reasons, including icing. Such instances affect the airspeed readings and the way the aircraft is flown, BBC reported.

Tjahjono said his agency was asking Boeing, the manufacturer of the plane, and the United States what action to take to prevent similar problems around the world. “If there are urgent findings to be delivered, we will convey them to the operators and to the manufacturer,” he said, according to AP.

On October 27, the plane had descended from 39,000 feet to 30,000 feet while flying from Manado to Denpasar. The flight was then grounded for 12 hours. “Yes, we took time to fix the problem Manado to Denpasar to make sure everything was fixed,” Nyoman Rai Pering, head of Lion Air’s largest engineering facility, told The Guardian. “We replaced the part suspected by our engineer. I think the problem was with the angle of attack, which controls the stability of the aircraft.”

Indonesian authorities earlier this week extended by three days the search for the victims and the second black box of the jet.

Meanwhile, hundreds of grieving relatives aboard a pair of Navy vessels prayed at the site of the crash on Tuesday, AFP reported. Mourners threw bouquets and scattered flower petals into the Java Sea.