Britain’s airspace was closed under false pretences, with satellite images revealing there was no doomsday volcanic ash cloud over the entire country.
Skies fell quiet for six days, leaving as many as 500,000 Britons stranded overseas and costing airlines hundreds of millions of pounds.
Estimates put the number of Britons still stuck abroad at 35,000.
However, new evidence shows there was no all-encompassing cloud and, where dust was present, it was often so thin that it posed no risk.
The satellite images demonstrate that the skies were largely clear, which will not surprise the millions who enjoyed the fine, hot weather during the flight ban.
Jim McKenna, the Civil Aviation Authority’s head of airworthiness, strategy and policy, admitted: ‘It’s obvious that at the start of this crisis there was a lack of definitive data.
‘It’s also true that for some of the time, the density of ash above the UK was close to undetectable.’
The satellite images will be used by airlines in their battle to win tens of millions of pounds in compensation from governments for their losses.
The National Air Traffic Control Service decision to ban flights was based on Met Office computer models which painted a picture of a cloud of ash being blown south from the Eyjafjallajokull volcano.
These models should have been tested by the Met Office’s main research plane, a BAE 146 jet, but it was in a hangar to be repainted and could not be sent up until last Tuesday – the last day of the ban.
Evidence has emerged that the maximum density of the ash was only about one 20th of the limit that scientists, the Government, and aircraft and engine manufacturers have now decided is safe.
British Airways chief Willie Walsh always insisted the total shutdown went too far.
‘My personal belief is that we could have safely continued operating for a period,’ he said.
Mark Tanzer, chief executive of Britain’s ABTA, which represents British travel agents and tour operators, said about 100,000 stranded British travellers should have been returned home by Monday morning.
About 35,000 more will remain marooned until Friday, the group said.
‘While most flights are back to normal, and most stranded British passengers will be back by the end of this weekend, there is still quite a high level of disruption in some destinations.
‘In some areas of the world, there is a significant lack of air capacity to enable British people to be returned quickly,’ Tanzer said.
Many Icelandic airports are closed and though authorities say Eyjafjallajokull is now producing much less ash, they confirmed no signs of the eruption ending.