New rights for airline passengers have been unveiled by the European Commission.
They include rerouting travellers with rival carriers if a flight is delayed for more than 12 hours.
The rules also clarify what are considered exceptional circumstances for compensation.
For example, mechanical failures on board the aircraft do not count, but natural disasters and traffic control strikes do.
The Commission says the new rules, which are not likely to become law until 2014, will give a lot more certainty to airlines and passengers.
"It is very important that passenger rights do not just exist on paper," said EU transport commissioner Siim Kallas.
"We all need to be able to rely on them when it matters most - when things go wrong."
He added: "We know that the real priority for stranded passengers is just to get home. So our focus is on information, care and effective rerouting."
During the Icelandic ash cloud crisis in 2010, when no flights could take off in Europe for several days, there was much confusion about how much responsibility the airlines should carry for the welfare of its passengers.
Helen Kearns European Commission
Some airlines were initially very reluctant to cover passengers' costs, but threats from the European authorities brought them into line.
Ryanair recently lost a case in the European Court of Justice against a passenger who had a seven-day wait for a Faro-Dublin flight. She had spent nearly 1,130 euros (£968) on a hotel, food and transport. The court ruled that Ryanair should have fully compensated her.
There have also been some concessions to industry. Under the planned measures, airlines will have to pay for a maximum of three nights' hotel accommodation - although this does not apply to passengers with reduced mobility, unaccompanied children or pregnant women.
