Airlines are looking to secure compensation from European governments for the losses they suffered during the volcano crisis last week.

The International Air Transport Association (IATA) estimates that the flying ban imposed on most of Europe cost airlines more than US$1.7bn (£1.1bn, €1.27bn) in lost revenue.

IATA attacked the governments of Europe, accusing them of a lack of leadership and coordination when dealing with the crisis.

The association also described Europe's decision to close airspace based on theoretical modeling of the ash cloud as guesswork, and demanded that any future decisions to impose flying bans should not be made based purely on theoretical calculations.

"This is not an acceptable system, particularly when the consequences for safety and the economy are so large," Giovanni Bisignani, IATA's director general and CEO said.

"Governments have not taken their responsibility to make clear decisions based on facts.

"Instead, it has been the air navigation service providers who announced that they would not provide service. And these decisions have been taken without adequately consulting the airlines."

The UK-based Civil Aviation Authority (CAA) has been singled out for its handling of the situation, with Willie Walsh, chief executive of British Airways, being particularly vocal in his criticism of CAA.

Andrew Haines, chief executive of CAA, was forced to issue a statement defending the safety regulator's actions.

"The volcanic ash cloud over Europe created an unprecedented situation for aviation," he said.

"Of course we wanted to get Britain's skies reopened as quickly as possible but could not do this without establishing what was safe and what wasn't, based on robust scientific data from the current ash cloud."

He also denied suggestions that the CAA "bowed under pressure" from the airlines to reopen the UK airspace.

"Far from being pushed into decisions by airlines or Europe it was the CAA who led the way," he claimed.

Meanwhile, Irish budget carrier Ryanair has backtracked on its earlier threats to break EU law and not compensate the cost of food and accommodation for its stranded passengers overseas.

A spokesperson had claimed that Ryanair would not compensate passengers stuck for days at European destinations more than the price of their air fare - which in some cases could be as little as 10 euro (£8.70).

Ryanair's CEO Michael O'Leary said earlier this morning that the airline would comply with the EU's passenger rights legislation (EU261), but added that the laws were "unfair and absurd".

"The events of the last seven days, under which Europe's airlines were prevented from flying by the closure of European airspace highlight how absurd and discriminatory the EU261 regulations are towards Europe's airlines," he said.

"While competitor ferry, coach and train operators are obliged to reimburse passengers reasonable expenses, this reimbursement is limited to the ticket price paid to those operators.

"Yet the airlines are required by regulation to meet potentially unlimited expenses, in circumstances where there has been a catastrophic closure of European airspace over the past seven days, as EU Governments and Regulators wrongly applied a blanket ban on flights over European airspace."