European pilots say they will not be pressured into flying by cash-strapped airlines desperate to claw back money lost in the ash cloud chaos.
An association of flight crew unions which represents thousands of pilots across the continent says not enough is known about volcanic ash to risk flying through it.
Philip von Schoppenthau, Secretary General of the European Cockpit Association, said: “The scientific data is still insufficient today to determine what effect such light ash contamination would have on engine performance.
“Aircraft today are not actually certified to fly through volcanic ash and pilot training is not done in a way that would allow pilots to fly in such conditions.
“We have seen, in the past, cases, where for commercial reasons, a lot of pressure has been put on pilots and then some pilots may simply give in to that pressure. Safety needs to be the paramount concern of the industry in general.”
The International Federation of Airline Pilots also says decisions on returning to flight operations should be left to pilots alone and be based on safety concerns rather than being economically driven.