The budget airline Germanwings was accused on Friday of deliberately playing down the incident so that no investigation was launched for a year, by which time the black box and cockpit recorder information were no longer available.
Friday's Die Welt newspaper worked with public broadcaster NDR to dig up reports on the incident which could have ended in catastrophe – and yet was reported to the air safety authorities in such a harmless manner that no investigation was undertaken.
But pilot association Cockpit on Friday accused Germanwings of "irresponsible downplaying" of the incident.
Flight 753 from Vienna to Cologne on December 20, 2010 was starting to land when first the co-pilot and then the pilot became cripplingly nauseous and barely conscious, the report says.
“You land the bird, I can't fly anymore,” the 26-year-old co-pilot told the 35-year-old captain before reaching for an oxygen mask. His arms and legs had gone numb and he had the feeling he could no longer think clearly.
Yet as he took the controls, the pilot felt tingling in his hands and feet, began to get tunnel vision and became badly dizzy – all this as the plane began decending at more than 400 kmph.
A medical examination afterwards showed the captain had a blood oxygen level of around 70 percent, while that of his co-pilot was less than 80 percent. Healthy people have a blood saturation level of nearly 100 percent, while 70 percent is close to the level at which people pass out, Die Welt.
The co-pilot wrote in his report that the plane would have crashed into the ground in Cologne with 144 passengers and five crew – and eight tonnes of fuel. The captain said he was in fear for his life.
Yet they managed to land the plane without incident, and accompanied by emergency teams, it taxied off the runway and came to a halt, whereupon passengers watched as the two men were driven in an ambulance, said Der Spiegel magazine.
Although Germanwings submitted a report to the German Federal Bureau of Aircraft Accidents Investigation (BFU), the incident did not appear in the BFU's monthly bulletin and no further action was taken. Experts now believe this is because Germanwings – a subsidiary of Lufthansa – downplayed the event to avoid investigation.
Die Welt said that it was only a year later that experts received new information and started looking into what had happened – by which time no information from the black box and cockpit recorder remained.
A spokesman for Germanwings told Die Welt there had been no problem and the pilots had not suffered any reduction in their capacities.
But the paper said it had seen a medical report from Lufthansa referring to an examination of the co-pilot six months after the incident, which said he was fully capable of service – after six months of being incapable. He had undergone weeks of counselling.
It is though the bad air may have been due to de-icing fluid getting into the cockpit's air supply.
Contaminated cabin air was scheduled to be discussed by MPs in the lower house of parliament on Friday afternoon.