Travellers stranded abroad by the volcanic ash cloud returned to the UK in a trickle rather than a flood today as recriminations flew about the Government's handling of the crisis.
All UK airports reopened but many services were cancelled, with budget airline Ryanair unable to operate any flights at all.
A leading holiday company chief said the Government's response to the crisis had been "a shambles", while Conservative leader David Cameron accused ministers of "muddle and confusion".
Liberal Democrat leader Nick Clegg, whose three young sons were stranded in Spain, said there would have to be a "post-mortem" of the response to the crisis.
But as returning passengers spoke of how they "despaired" of ever getting home, Prime Minister Gordon Brown defended the time taken to reopen UK airspace, stressing that passengers had to be "safe and secure".
He added that the Government would never have been forgiven if aircraft had been allowed to fly when people's lives were at risk.
Transport Secretary Lord Adonis denied the decision to reopen UK airspace - made by the Civil Aviation Authority (CAA) last night - had been based on pressure from airlines.
And CAA chief executive Andrew Haines said he "made no apologies" for UK airspace being closed for so long and added that any inquiry into the crisis would support the CAA's actions.
Most carriers were able to run only a limited services today, with Ryanair flights not starting again until 1pm tomorrow.
One of the first to arrive at Heathrow airport today was Narinder Panesar, from Coventry in the West Midlands, who arrived on a Continental Airways' flight from Newark, USA.
Mrs Panesar, who was travelling with her husband Jasbir and their two daughters, said: "It feels so good to be home and to be safe. We were just despairing."
British Airways, whose chief executive Willie Walsh said he did not believe the "blanket ban" on airspace had been necessary, said it would take time to return to a "full flying programme" as many of its planes and crew were out of position.
Virgin Atlantic flew a full schedule today but many carriers will not be getting back to something like normal until tomorrow.
With the cost of the shutdowns likely to run into billions of pounds and with an estimated 150,000 stranded Britons to be repatriated, there was mounting criticism of the way events had unfurled.
Peter Long, chief executive of Tui Travel which includes holiday companies Thomson and First Choice, said: "The Government's response to the crisis has been a shambles. It is clear that they under-estimated the severity of the consequences of the decision for a blanket closure of the airspace for such a protracted period of time."
The crisis has been handled "with the mentality of the early 20th century", with 21st century requirements not being recognised, Jean-Claude Baumgarten, president and chief executive of the World Travel & Tourism Council said.
There was also criticism from airlines about the EU regulation which requires EU carriers to cover stranded passengers' reasonable expenses.
Ryanair chief executive Michael O'Leary said he would defy the rules, with Ryanair reimbursing travellers the original price of their air fare and no more.
Mike Carrivick, chief executive of the Board of Airline Representatives which represents more than 90 airlines, said the EU regulations were "unfair" and were never intended to cover cases such as the ash cloud crisis.
Those still stranded abroad were coping as best they could, with Foreign Office Minister Chris Bryant admitting that it was "phenomenally complicated and difficult" getting everyone home.
Speaking in Madrid to where Britons were being urged to travel to take coaches home, Mr Bryant added: "I really don't want to pretend that we can do everything because we can't. The main thrust now has to be by the airlines and tour operators."
Thomson and First Choice said they hoped to get 21,000 stranded holidaymakers home today and that the majority of their clients who had extended stays overseas would be back in the UK by Friday.
Budget carrier easyJet, which ran about 86% of its scheduled operations today, said it was launching 15 special rescue flights to bring back stuck tourists.
Network Rail and train companies announced that rail services between London and Heathrow, Gatwick and Stansted stations would remain open all night as would Gatwick Airport station and three main London stations - Paddington, Liverpool Street and Victoria.
Planned weekend engineering work on the main London to Scotland routes - the East Coast and West Coast main lines - has been cancelled.