Flights have landed at a number of UK airports for the first time in six days following the lifting of restrictions caused by a volcanic ash cloud.

The Civil Aviation Authority allowed a phased reopening of airspace after a reassessment of the risk to aircraft.

It said its safety tests showed that plane engines had “increased tolerance levels in low ash density areas”.

BAA, which operates many of the UK's airports, said people should contact their airlines before travelling.

“Not all flights will operate during the early period of opening, and we will do everything we can to support airlines and get people moving,” a spokesman said.

Some restrictions will remain on flights in UK airspace, but they will be much less stringent than before.

Dame Deirdre Hutton, of the Civil Aviation Authority (CAA), said there had been detailed consultation with experts to reassess the tolerance of planes to the ash cloud.

There will be plenty of time for a post mortem of what has happened

Willie Walsh
British Airways chief executive
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The CAA said it was a “situation without precedent” and that decisions had been made based on “thorough gathering of data and analysis”.

“The major barrier to resuming flight has been understanding tolerance levels of aircraft to ash,” the CAA said.

“Manufacturers have now agreed increased tolerance levels in low ash density areas.”

Transport Secretary Lord Adonis, who made the initial announcement, denied the decision to reopen airspace was the result of pressure from the airline industry.

He told BBC Two's Newsnight programme: “The issue at stake here has been the assessment of the safety authorities as to what is the safe way in which planes can fly when there is a presence of ash.

“The fact which has changed in the last week is we have had a volcanic eruption and having to assess safe levels of ash content in the atmosphere within which planes can fly has been an urgent issue which the safety authorities have had to deal with.”

Prime Minister Gordon Brown said: “This solution has been reached as a result of the close working between the government, the Civil Aviation Authority, airlines and the manufacturers, and will allow the thousands of UK citizens stranded abroad to return home to their families.