Investigators have suggested that low levels of airport traffic could have reduced the alertness of an Airbus A350 crew before the aircraft took off without clearance from Barcelona.

The Singapore Airlines A350 (9V-SMU), operating to Milan Malpensa as part of an onward service to Singapore on 24 October last year, was instructed to line up and wait on runway 07R.

After giving the instruction, the tower controller communicated with a business jet which had just landed on runway 02 – a runway whose approach path requires overflying 07R.

The controller also intended to allow a trailing aircraft, an Airbus A320, to land on 02 before clearing the A350 for departure.

But while the controller was speaking to the business jet crew, he saw the A350 rolling for take-off.

SIA A350-900-c-Airbus

Source: Airbus

Pilots of the A350 believed they had received take-off clearance but none had been recorded

Singapore’s Transport Safety Investigation Bureau says the controller opted against ordering the aircraft to abort its take-off, after assessing that safe separation with the A320 could be maintained. The aircraft did not come within 2.8nm of one another.

The inquiry says the A350 crew, on the ground radio frequency, would not have heard the tower communications with the approaching A320, and did not see the preceding business jet land because they were facing in a different direction during taxiing.

Had either of these situations been different, it states, the crew “might have paid more attention” to the runway 02 traffic.

“The flight crew recalled having received the take-off clearance,” the bureau says, but adds that air traffic communications records show no such clearance was given.

“Other than the flight crew’s ‘line up and wait’ readback, there was no other readback by the [pilots]. Based on the evidence collected, the investigation team would have to discount their recollection.”

Neither pilot was able to explain why they might have heard a take-off clearance.

Investigators state that, as the A350 was about to enter the runway, the approaching A320 should have been within range on the pilots’ navigation display.

But the senior first officer, who was flying the A350, testified that he did not see any aircraft on approach to 07R – either visually or on the navigation display – nor any other aircraft in the vicinity.

Weather conditions and the daylight visibility were good.

Activity at Barcelona was suppressed as a result of the pandemic-driven air transport crisis. The A350 only had 28 people on board.

“The flight crew had believed that they were the only aircraft traffic in the vicinity,” the inquiry states.

“Low workload in traffic monitoring due to the low [airport] traffic could have resulted in some form of reduced alertness by the flight crew.”