Many UK airports are closed until 0100 BST on Monday
Airlines have criticised the latest decision to ban flights at a raft of UK airports because of volcanic ash.
Sir Richard Branson, president of Virgin Atlantic, said the closure of Manchester airport was "beyond a joke".
A BA spokesman said the bans were "not justified on safety grounds" and called for airlines, not authorities, to be responsible for the decision.
But the Civil Aviation Authority said all the airlines had agreed "on the way forward" at a conference on Friday.
The authority uses Met Office data to set out no-fly zones in the UK.
Manchester, Liverpool, East Midlands and Doncaster airports are among those that have been closed since 1300 BST, with Birmingham and Norwich having shut at 1900.
Airports in Northern Ireland, Prestwick near Glasgow, some Scottish islands and the Isle of Man are also affected as volcanic ash from Iceland drifts across the UK.
Many are not due to reopen until 0100 BST on Monday at the earliest.
Ash from the Eyjafjallajokull volcano has caused disruption to thousands of flights since April, when airspace across Europe was shut down for five days over concerns ash could turn to molten glass in high temperatures, crippling plane engines.
Scientists and engineers have since revised the safe-to-fly threshold, however clouds of volcanic ash have continued to drift over Europe, causing airport closures, flight delays and cancellations.
However, Sir Richard said tests by airlines, aircraft and engine manufacturers showed there was "no evidence" planes could not continue to fly "completely safely".
"Over 1,000 flights took off from France last week in similar conditions to that which exist in Manchester today without encountering any problems or showing any levels of ash concentration," he said on Sunday.
"We need strong leadership to intervene to avoid doing further unnecessary damage to the UK economy and lives of travellers."
A Civil Aviation Authority spokesman said Sir Richard's remarks were "quite surprising bearing in mind we had all the airlines and manufacturers into a conference on Friday, including Virgin".
"They all agreed the way forward including his airline," the spokesman said.
The problem this time round is it's much denser, it's at a higher altitude, nearly 30,000ft, and no one wants to take the risk - not least an airline - for being the one that has a problem should something go wrong
He stressed that everyone was working together to find a way to raise the threshold level of ash considered safe for flying.
But a British Airways spokesman said the airspace authorities were being "overly restrictive" and the airline had "no confidence" in the model being used as a basis for deciding on airspace closures.
"While we welcome the steps that have been taken since mid-April to moderate the restrictions, it is clear there is too much reliance on the theoretical model of ash spread produced by a single body - the London Volcanic Ash Advisory Centre.
"As a global airline, British Airways has operated for many years in areas of volcanic activity, and we believe airlines are best placed to take the final decisions on whether or not it is safe to fly," he said.
The Met Office, which operates the London Volcanic Ash Advisory Centre, said the model was "well proven" and provided results "consistent" with other models, such as those in France and Canada.
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"It has shown over many incidents - not only volcanic eruptions - it works very well. It is a sophisticated model, which retains residual ash - so it's not just a snapshot of what's erupting now, but provides a fuller picture of what's in the atmosphere," a spokesman said.
"It is important to remember the Met's role is to provide forecasts to standards and tolerances set by regulator," he added.
Paul Charles, an aviation analyst and the former head of communications at Virgin Atlantic, said the airline industry was voicing its "anger and frustration" as it faced more uncertainty and "its worst peace-time crisis".
He said the industry had lost £1bn during the flight bans in April, and there was a danger "many more million pounds" would be lost.
The "number one cardinal rule" in the airline industry was safety, he said, but the problem was there were so many different views - from forecasters, operational teams and airlines - that some believed it was "perhaps possible to fly through this ash cloud".
"The problem this time round is it's much denser, it's at a higher altitude, nearly 30,000ft, and no-one wants to take the risk - not least an airline - for being the one that has a problem should something go wrong," he said.
For passengers, it was a "very bad week" to travel, he added.
BA is facing industrial action in the coming days, potentially adding to travel disruption.