Both pilots and all four cabin crew on this brand-new Germanwings Airbus A319 began feeling "sleepy and unwell" after only a few minutes of flight, according to the report from the Irish Air Accident Investigation Unit. Donning oxygen masks provided almost instant relief from the symptoms.
The purser, the first to act on her awareness of what she saw and felt by calling the pilots on the interphone, may have saved the day by doing so. An "unusual number "of passengers were falling asleep and her attempt to attract the attention of a nearby cabin crew member failed. He was "unresponsive".
Her message jolted the pilots into the realisation that they, too, were feeling unwell. They declared a full emergency and returned to Dublin, landing just 24min after take-off.
An extremely thorough investigation into what happened checked out the aircraft and engines and found no evidence of any contamination.
What they didn't do - and that's a real pity - is to check out the passengers, except by interviewing them. Blood tests, even a few days later, may have provided the missing evidence of what happened.
The AAIU's principle recommendation was that Ireland's major airports should, as required by ICAO, have medical staff on hand. Dublin did not.
But it requires more than an available doctor. It requires crew and passengers who know they have been affected by some form of cabin air contamination to insist on having medical tests.
Well done the Purser. If the crew just quietly gone to sleep we could have seen a repeat of the Helios accident. That was caused by crew and passenger hypoxia following failure of the cabin to pressurise - not the case here. But the risk of subtly losing consciousness, however it happens, needs to be taken seriously.