On the same day late last month the European Union (EU) Aviation Safety Agency (EASA) and the UK Civil Aviation Authority (CAA) both authorised the return to service of the Boeing 737 MAX commercial aeroplane. Both agencies required modifications to the airliner and the associated maintenance and training procedures. Commercial aviation regulators in the US, Brazil and Canada had already cleared the 737 MAX to return to service, also with provisos that certain technical and software modifications and upgrades were made to the aircraft and its associated maintenance and training procedures.

“We have reached a significant milestone on a long road,” said EASA executive director Patrick Ky. “Following extensive analysis by EASA, we have determined that the 737 MAX can safely return to service. This assessment was carried out in full independence of Boeing or the [US] Federal Aviation Administration [FAA] and without any economic or political pressure – we asked difficult questions until we got answers and pushed for solutions which satisfied our exacting safety requirements. We carried out our own flight tests and simulator sessions and did not rely on others to do this for us.”

“Our thoughts remain with those affected by the tragic accidents of the Boeing 737 MAX,” assured UK CAA CE Richard Moriarty. “This is not a decision we have taken lightly and we would not have allowed a return to service for UK operators, or lifted the ban on the aircraft operating in UK airspace, unless we were satisfied that the aircraft type is airworthy and can be operated safely. The international work to return the Boeing 737 MAX to the skies has been the most extensive project of this kind ever undertaken in civil aviation and shows how important the cooperation between States and regulators is to maintaining safety.”

The 737 MAX was grounded worldwide in March 2019, as a result of two accidents within six months, which killed 346 passengers and crew. The fundamental cause of these disasters was ascertained to be the aircraft’s Manoeuvring Characteristics Augmentation System (MCAS). Ironically, this was meant to make the aeroplane easier to handle. But it received its data from just one angle of attack sensor and if that malfunctioned, the MCAS would repeatedly activate itself and push the nose of the airliner down. That was what had happened in both accidents, with the pilots ultimately losing control of their aircraft.

“We have every confidence that the aircraft is [now] safe, which is the precondition for giving our approval,” stated Ky. “But we will continue to monitor 737 MAX operations closely as the aircraft resumes service. In parallel, and at our insistence, Boeing has also committed to work to enhance the aircraft still further in the medium term, in order to reach an even higher level of safety.”

The UK CAA made use of detailed information from EASA, the US Federal Aviation Administration and Boeing in reaching its decision to lift the grounding of the 737 MAX. In particular, the British agency worked with EASA (the UK CAA was a member of EASA until 23:00 London time on December 31, 2020, when Britain’s departure from the EU came into full force). EASA served as the UK’s technical agent regarding the 737 MAX and, being the UK’s validating authority, the CAA reviewed its work. The UK CAA had full view of all EASA’s technical assurance activities regarding the Boeing airliner. The British also took part in simulator evaluations and the forums on pilot training.

The required physical changes to the 737 MAX were the same for all these regulatory agencies, so that there would be no technical or software differences between those aircraft operated by European and North American operators. However, EASA’s requirements did have two main differences to those of the FAA. EASA explicitly permitted pilots to stop a ‘stick shaker’ (a type of warning system) from vibrating if it was activated in error by the MCAS (to ensure that it did not distract the crew). And EASA banned certain high-precision landings by the 737 MAX (this was expected to be a temporary restriction).