The Met Office unnecessarily triggered the six-day closure of British airspace which has cost passengers, airlines and the economy more than £1.5billion, according to senior officials.
A scientific model based on ‘probability’ rather than fact was used by the government agency to forecast the spread of the volcanic ash cloud, according to critics.
Matthias Ruete, the European Commission’s director general of transport, said air traffic authorities should not have imposed a widespread ban.
He suggested the ban should have been restricted to a 20 to 30 mile limit around the volcano in Iceland.
He said: 'The science behind the model we are running at the moment is based on certain assumptions where we do not have scientific evidence. It is a black box in certain areas.'
Results of 40 or so European test flights over the weekend, including a British Airways flight on Sunday, suggested the risks were not as high as computer models predicted
None found evidence of any ash in engines, windows or lubrication systems.
'We don’t even know what density the cloud should be in order to affect jet engines. We have a model that runs on mathematical predictions.
'It is probability rather than actual things happening,' Mr Ruete said.
However, NATO have taken the ash threat seriously enough to limit military exercises after volcanic glass built up in fighter engines.
A spokesman from the UK Met Office said while computer models were used to make forecasts, they were being checked against actual evidence.
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