EU rules mean delayed holidaymakers can now claim money from airlines. But legal battles are being fought to decide when these rights apply.
Airline passengers are facing a multi-billion pound fight for compensation for delayed or cancelled flights.
Two potentially landmark cases are currently being heard by UK courts.
Their outcomes could affect thousands and perhaps even millions of travellers who have been delayed or stranded at airports over recent years.
The first of the two major current cases, Huzar versus Jet2.com, concerns when an airline can avoid paying compensation because a delay was the result of "extraordinary circumstances".
For example, if bad weather keeps aircraft grounded, passengers will not be entitled to redress as the airline is not at fault.
In this case, Mr Huzar’s flight from Malaga to Manchester in October 2012 was delayed after the aircraft developed a fault on its approach to Malaga.
Jet2 says this technical fault was an extraordinary circumstance and no compensation is payable, while Mr Huzar says that such issues are inherent in the running of an airline.
Mr Huzar lost his case originally, but the decision was overturned on appeal at Manchester County Court last autumn. Jet2 is now appealing that verdict.
Sam Borrett from solicitors Bott & Co, which is representing Mr Huzar, says: "In our experience approximately 90% of disputes are around technical defects.
"Therefore the outcome of this case will have a huge impact on the number of flights that are eligible for compensation."
‘Hundreds of cases in pipeline’
The firm estimates that a win for Mr Huzar could open the door to more than £6 billion of similar claims.
Borrett adds that in many cases, airlines are passing off the likes of faulty microwaves and blocked toilets as extraordinary circumstances, and turning down claims as a consequence.
He says: "There are hundreds of cases stayed in the UK legal system pending the outcome of this case, with many more people waiting to issue proceedings dependent upon the judgment."
The second ongoing case relates to how long consumers have to bring claims.
How long do you have to claim?
In the case of Dawson versus Thomson Airways, which Bott & Co is also involved in, the airline says that under the Montreal Convention passengers have just two years in which to make a claim, as opposed to the six years typical in UK law.
The original case was decided in Mr Dawson’s favour at Cambridge County Court last summer, but Thomson has now asked the Court of Appeal for a second opinion.
Borrett says that if the Court of Appeal upholds the Cambridge decision, it could mean up to an extra £4 billion compensation being claimed.
How compensation works
Current compensation calculations are based on the length of any delay and the distance due to be travelled.
All flights must be with an EU-based carrier, or should have taken off and landed within the EU to be eligible.
For flights of up to 1,500km, €250 (roughly £205) can be claimed for delays of more than three hours. This rises to €400 (£330) for distances between 1,500km and 3,500km.
For flights farther than 3,500km, €300 (£245) can be claimed for delays between three and four hours.
Anything more than four hours means a possible €600 (£490) compensation.
Bott & Co’s website has a free compensation claim calculator
: type in the date and number of any flight you have been delayed on to check if you have a potential case.