An error caused the TUI 737 flight to be aborted in mid-air

An investigation found that a TUI plane with 193 people on board failed to pressurize after engineers failed to turn the switches back on following maintenance.

The Boeing 737-8K5 took off from Manchester Airport on October 17, 2023, bound for Kos, Greece, but only reached north Lincolnshire before the pilot was ordered to abort.

The Air Accident Investigation Branch (AAIB) found that both pilots failed to notice the oversight during checks and did not fully follow protocols when alerting.

The jet returned to Manchester with no reported injuries, but investigators said it was likely the passengers were “at progressive risk of hypoxia.” The BBC has contacted TUI for comment.

Just three days later the same plane came off the runway at Leeds Bradford Airport during Storm Babet, with the cause determined to be a “catastrophic failure” of a nose wheel bearing.

According to a Report of the incident over Lincolnshirethe aircraft departed “with the engine bleed air system turned off” because the switches had been “incorrectly turned off after maintenance work” the night before.

The switches were not switched on during the pre-flight checks either.

“The after-takeoff checklist was intended to detect the latter failure, but the incorrect switch selection went undetected by the crew,” the report said.

The engineer who carried out the work told AAIB investigators that they believed the switches had been turned back to “on” after the work was completed.

A second technician was also unable to identify the incorrect switch position.

As a result, the aircraft failed to pressurize, the report said, and the crew failed to perform required drills outlined in a Quick Reaction Handbook (QRH) in response to a cabin altitude warning “that remained illuminated for 43 minutes.”

A QRH contains checklists, including how to respond to an “abnormal” event. The cabin altitude checklist includes “immediate use of oxygen masks.”

The pilot turned both switches to “on” and “continued the climb,” the report said.

Another warning was activated, prompting the pilot to abort the climb and seek advice from superiors on the ground.

The decision was made to return to Manchester Airport with “the situation explained to passengers over the public address system”, the report said.

Investigators found that if the plane, carrying six crew members and 187 passengers, had continued to climb, the passengers’ oxygen masks would have opened automatically at an altitude of 14,000 feet (4,267 m).

The likelihood of loss of consciousness below 14,000 feet is “very low” for people without serious medical conditions, the report said.

However, “cognitive performance and decision-making” could be impaired at this level, it continues.

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