A TUI passenger plane was involved in a “serious incident” while flying over the Humber region, just three days before the same plane suffered an unrelated “catastrophic failure” while landing at Lees Bradford Airport, according to a report.

A new report published by the Air Accident Investigation Branch examined the North Lincolnshire incident. The Boeing 737-8K5 took off from Manchester Airport shortly after 6am on 17 October 2023. It carried 187 passengers and six crew; No one was injured in the incident. The plane landed safely in Manchester at 8.10am.

Just minutes after takeoff, while flying into Kos Airport, Greece, the cabin altitude warning alerted the pilot to a cabin pressure malfunction.

The “serious incident” report said: “Both engine bleed air systems had mistakenly been released for takeoff, so the aircraft was unable to pressurize.”

Engineers reportedly turned off the systems during previous maintenance but did not turn them back on during pre-flight checks of the aircraft.

The crew elected to turn both systems back on and continued to fly higher into the sky, believing the problem was resolved. However, during the climb the main warning light came on, indicating a malfunction. After consulting the operator’s maintenance check, the Commander decided to return to Manchester Airport as a safety precaution.

Since the plane was too heavy to land, he had to enter the hold to burn fuel and reduce the weight of the plane. The crew did not complete their specific drills in response to the cabin altitude warning (such as wearing an oxygen mask), which remained on for 43 minutes. HullLive reports.

The report explained the risk of hypoxia, which means low oxygen levels in the blood, and made the following statements: “Since there was no pressure on the aircraft, the crew and passengers were exposed to the risk of hypoxia. At cabin altitudes above 10,000 ft but below 14,000 ft, due to the pre-existing significant medical problems.” The possibility of loss of consciousness is very small.

“However, exposure to hypoxia in this altitude window may be sufficient to affect cognitive performance and decision-making to the point where decline can be observed on cognitive tests.

“Within this altitude range, there are many variables that affect the severity and impact of hypoxia, including duration of exposure, rate of onset of hypoxia (e.g. rate of climb if not pressurized), physical workload, fatigue, individual responses, and the type of task performed.”

“It is also difficult to separate the relative contribution of hypoxia in this altitude range from other performance-impairing factors such as fatigue, distraction, or other human performance problems.”

The report stated that the plane’s climb was interrupted due to the warning of the air conditioner. If the plane had continued to climb, he said, “the aircraft’s passenger oxygen system would have automatically activated when the cabin altitude reached 14,000 ft.”

Once cabin altitude of 15,800 ft was reached, the pressurization automatic failure master alert would be triggered. The report added: “As exposure to hypoxia increased, the crew would become less likely to take proper recovery measures.”

The report also stated that the pilots were not initially scheduled to fly this aircraft and that they would leave reserve duty at 3 a.m. The commander, who was awakened at 1am by a notification on his smartphone’s roster app that he had been assigned to fly from Manchester to Kos, reportedly had only three hours of sleep the night before and had worked “significant overtime”. “missions” for the previous eight weeks.

The co-pilot was notified by a phone call from the crew at 02:30. Both pilots were given a reporting time of 4.30am.

While these may not be individually tiring, cumulative disruption could be a factor, the report notes. The letter said: “Although the Commander does not believe fatigue was a factor in this incident, analysis of his squad over the eight weeks prior to the incident and the rest period immediately preceding the incident indicate that fatigue may still have been a contributing factor. “Fatigue, especially chronic fatigue, is one’s own ability to recognize symptoms.” It should be noted that he may be too insidious to do anything.”

Three days later, the same aircraft left the runway while landing in the middle of Storm Babet at Leeds Bradford Airport. While there was minor damage to the plane, no one on board was injured.

TUI has been approached for comment.