What happened
On 22 September 2025, a FlySafair Boeing 737-800, registered ZS-SJU, was operating a scheduled commercial flight from Chief Dawid Stuurman International Airport to Cape Town International Airport. The flight, carrying 185 passengers and six crew members, had climbed to a cruising altitude of flight level 360.
While passing abeam George, the aircraft experienced a loss of automatic cabin pressure regulation. This triggered the cabin altitude annunciator and an associated aural warning. In response, the flight crew donned oxygen masks, and the passenger oxygen masks deployed automatically. The captain took control of the aircraft and requested an emergency descent to flight level 100 from Cape Town approach control.
During the descent, the first officer tested the manual mode of the cabin pressure control, which functioned correctly and allowed the pressure to stabilize. After leveling off at 10,000 feet, the crew removed their masks and continued the flight. Upon arrival at Cape Town, the aircraft initially performed a missed approach due to excessive approach speed but eventually landed safely on Runway 19. No injuries were reported among the passengers or crew.
The investigation
The SACAA AIID investigation focused on the mechanical failure that led to the depressurization. Investigators examined the aircraft's technical documentation, confirming that the Boeing 737-800 had been properly maintained and had recently undergone a phase inspection. The crew's licenses and medical certificates were also verified as valid and in order.
Findings
The investigation established that the decompression was triggered by a latent internal failure of cabin pressure controller 1. This specific failure prevented the aircraft from maintaining automatic pressurization and, crucially, blocked the system from successfully transferring control to the alternate controller. This dual-failure mechanism resulted in the loss of automatic pressure regulation during the cruise phase.