AAIB investigation to Boeing 737-86N, G-NPTA
Loss of cabin pressurisation, approaching Edinburgh Airport, 17 May 2025
The aircraft was flying between East Midlands (EMA) and Edinburgh (EDI) Airports. Due to the quantity of dry ice forming part of the cargo load, the operator’s procedures required the aircraft’s air conditioning pack control switches to be in the high position for the flight. The commander described this as “an unusual [pack] configuration.”
Approaching top of descent the cabin altitude warning sounded, prompting the flight crew to don oxygen masks and execute an emergency descent. After levelling off, the commander checked the overhead panel and found both pack switches were selected off. Switching them back on restored pressurisation and the flight continued into EDI.
The commander was convinced they left EMA with the packs operating and had not noticed any switches out of place when conducting a scan of the overhead panel at the top of climb. He concluded the switches must have been selected off during flight, however neither he nor the co-pilot recalled doing so. The commander considered it possible the switches had initially been in the normal on position and that the wrong “unusual configuration” (ie off rather than high) had been selected to “correct what [they] perceived as a mistake.”
Download the report:
Download glossary of abbreviations: