Global airlines have lost about $1.7bn (£1.1bn) of revenue as a result of the disruptions caused by the Icelandic volcanic eruption, a body has said.
The International Air Transport Association (IATA) said that at its height, the “crisis” hit almost a third of global flights.
It also estimated that 1.2 million passengers a day were affected.
On Tuesday night, flights started landing in the UK after a six-day shutdown of UK airspace.
The decision to lift the ban followed safety tests that showed plane engines could cope in areas of low density ash.
IATA noted that airlines had saved about $110m a day on fuel while planes were not flying, but said they had also faced additional costs from looking after stranded passengers.
“For an industry that lost $9.4bn last year and was forecast to lose a further $2.8bn in 2010, this crisis is devastating,” said Giovanni Bisignani, chief executive of IATA.
Mr Bisignani also criticised governments for the haste with which they closed airspace, and called on them to provide compensation to the airlines.
“Airspace was being closed based on theoretical models, not on facts. Test flights by our members showed that the models were wrong.
“[The crisis] is an extraordinary situation exaggerated by a poor decision-making process by national governments. Governments should help carriers recover the cost of this disruption.”