Days after a TransAsia Airways plane with 58 people on board crashed into a river in Taipei, the airline announced that all of its pilots who fly ATR planes will undergo mandatory proficiency tests, according to media reports. The announcement comes after preliminary investigations suggested that the pilots may have accidentally shut down one of the ATR 72-600 aircraft’s engine after the other one lost power.

“Starting today, all of TransAsia's 71 ATR pilots will undergo tests to be carried out by the CAA (Civil Aeronautics Administration) and third-party professional units for an estimated period of four days,” the airline reportedly said in a statement released Saturday.

The airline also said that it has cancelled 90 domestic flights for the next three days as its pilots undergo the tests ordered by Taiwan's Civil Aeronautics Administration, according to media reports.

Although investigators are still trying to piece together the series of events that led to the crash, preliminary analysis of the flight data recorders indicated that both engines of the plane had failed prior to the crash. While the first engine went idle 37 seconds after takeoff, the second one was shut down 46 seconds later. Investigators suspect that the pilots might have turned off the second engine in a bid to restart both engines, a move that aviation experts say could have been a mistake.  

Wednesday’s crash, which killed at least 35 people, was the airline’s second fatal accident in seven months. In July last year, another TransAsia plane, also an ATR-72 model, had crashed off the west coast of Taiwan as it attempted to land in bad weather. Forty-eight people were killed in the accident.