TUI Flight Aborted Mid-Air After Cabin Fails to Pressurize Due to Maintenance Error

An investigation has determined that a TUI aircraft, carrying 193 individuals, experienced a failure to pressurize its cabin because engineers neglected to reactivate switches after completing maintenance work. The Boeing 737-8K5 departed from Manchester Airport, bound for Kos, Greece, on October 17, 2023. However, the flight was instructed to abort its journey while over northern Lincolnshire. The Air Accidents Investigation Branch (AAIB) concluded that both pilots did not identify the omission during pre-flight inspections and subsequently failed to follow established protocols upon receiving an alert. The aircraft returned to Manchester, with no reported injuries. Nevertheless, investigators indicated that individuals on board “were exposed to a progressive hypoxia risk.” The BBC has reached out to TUI for a statement regarding the incident. Merely three days subsequent to this event, the identical aircraft deviated from the runway at Leeds Bradford Airport amidst Storm Babet. A “catastrophic failure” of a nosewheel bearing was identified as the underlying cause. A report concerning the Lincolnshire incident stated that the aircraft took off “with the engine bleed air system off” because the switches had been “incorrectly left off following maintenance activity” conducted the preceding night. Furthermore, the switches were not activated during the pre-flight inspections. The report specifies: “The after take-off checklist is designed to trap the latter omission, but the incorrect switch selection went undetected by the crew.” The engineer responsible for the maintenance informed AAIB investigators that they believed the switches had been reset to the “on” position upon completion of the work. A second engineer similarly did not identify the incorrect switch setting. Consequently, the aircraft did not pressurize, according to the report. Additionally, the crew did not execute the required procedures from a Quick Reaction Handbook (QRH) when a cabin altitude warning, “which remained illuminated for 43 minutes,” was triggered. A QRH provides checklists, detailing responses to “non normal” events. The specific cabin altitude checklist mandates the “immediate use of oxygen masks.” The report indicates that the pilot moved both switches to the “on” position and “continued to climb.” An additional warning subsequently activated, leading the pilot to halt the ascent and consult with ground control. The determination was made to return to Manchester Airport, and the “situation explained to the passengers over the public address system,” as per the report. Investigators observed that if the aircraft, which had six crew members and 187 passengers on board, had proceeded with its climb, the passenger oxygen masks would have automatically deployed at 14,000ft (4,267m). The report specifies that the probability of losing consciousness below 14,000ft is “very small” for individuals without significant medical conditions. Nevertheless, it further notes that “cognitive performance and decision-making” could be impacted at this elevation.