Partial suspension of Boeing 737 Max operations exposed an extraordinary regulatory disparity, with European and US authorities – normally fixated on procedural harmonisation and alignment – entrenched in opposing positions on the matter.

Even within Europe the situation had started to appear confusing, with some carriers opting for a precautionary halt to Max operations in contrast to the wait-and-see approach adopted by national and supranational regulators regarding the investigation into the Ethiopian Airlines accident.

The UK Civil Aviation Authority's halt to Max services on 12 March was unilateral and not co-ordinated with the European Union Aviation Safety Agency in advance.

French, German and Irish air transport regulators similarly imposed restrictions on the aircraft, a domino-chain of individual decisions which culminated in a formal – and seemingly inevitable – EASA response, 6h after the UK deadline, ordering the grounding of Max 8s and 9s.

EASA's suspension order became the most significant for the aircraft, and one which effectively undermined the US FAA, the original certifying authority, exposing a serious inconsistency in the two sides’ approaches to the situation.

The FAA had staunchly defended the aircraft, insisting it had no evidence of any "systemic performance issues" and that its analysis "provides no basis" to order a grounding.

"Nor have other civil aviation authorities provided data to us that would warrant action," it stressed, essentially stating that the action by EASA and other regulators, as well as individual airlines, was based on suspicion rather than fact.

Without firm recorder data the crash has presented a fundamental dilemma to both regulators and operators as to whether uncertainty alone, in the face of insufficient hard evidence, justifies the drastic measure of a mass grounding, particularly when the conditions for lifting such a suspension have yet to be clarified.

Both arguments, for and against a grounding, are understandable. Disunity over an issue as fundamental as the safety of a newly-certified aircraft design is not.

The paradoxical nature of the regulatory disparity became clear when, at one point, two Max operators found themselves taking opposing measures – one complying with a suspension, the other able to fly without restriction – while simultaneously maintaining that they were prioritising passenger safety.

Boeing and the FAA, having held out almost to the point of ridicule, needed a face-saving reason if they were to perform a reverse-ferret and, in the absence of recorder information, found one in a vague reference to “refined satellite data”.

Caution previously considered unnecessary was suddenly in abundance, and the US side duly fell into line. But not soon enough to avoid the perception that the tails of political interests might be wagging some regulatory dogs.

Little elaboration has emerged as to why this satellite data, in itself, was sufficient to dislodge a fervent conviction that the 737 Max was sound. One enigmatic, probably unanswerable, curiosity is whether the same data would have prompted a unilateral grounding order by the FAA if there had been no rising tide of bans and prohibitions from other regulators. And if not, why not?

While some 7,300 Boeing 737s from the -700 upwards have been delivered, only 5% are Max variants.

This lack of critical mass for the revised and re-engined aircraft, combined with short in-service period and a 132-day interval between two serious accidents, has contributed to a distrust which, fanned by social media, threatens to surpass that which emerged after 737 rudder 'hard-over' accidents in the early 1990s. Confidence and consistency in regulatory authority, as a result, has seldom mattered more.

Source: Flight International