Airlines are at risk of breaking consumer law by imposing rip-off ‘no show’ clauses – which they can use to cash in when a passenger misses the first leg of their journey.

The clauses – often buried in airline terms and conditions – mean passengers who miss an outbound flight can be considered a ‘no-show’.

All their connecting or return flights are then cancelled, typically with no refund given, and their seats can be resold – allowing the airlines to double their money.

The accusation came today from consumer organisation Which? which claimed that passengers often only find out their tickets have been cancelled when they arrive at the airport for their return leg. They are then forced to buy another seat at a vastly inflated price, or pay a hefty fine – up to €3,000 in some cases – to use their original ticket.

One traveller who contacted Which? told how she was forced to pay Virgin Atlantic an extra £1,354 to get home from New York – more than the £1,284 price of her original return flight – after she missed a flight from London and the airline imposed its ‘no show’ clause.

After finding that 11 out of the 16 airlines that Which? looked at used the clauses, the consumer group has written to nine carriers – including British Airways and Virgin Atlantic – informing them that the practice is potentially in breach of both the Consumer Rights Act and the Unfair Terms in Consumer Contracts Directive.

After an initial approach by Which?, two carriers – Thomas Cook Airlines and Channel Islands minnow Aurigny – plan to drop their ‘no show’ clauses.

Which? is joining forces with consumer groups in nine countries across Europe to stamp out the unfair practice.

Watchdogs in the Netherlands and Greece are today announcing court action against KLM, who along with Air France, have some of the harshest ‘no show’ terms, according to Which?. The two airlines are already involved in a legal battle with Belgian consumer group Test Achats/Test Aankoop.

The case for industry-wide change is strengthened by a UK court case last year, in which a passenger won compensation from Iberia, owned by BA parent International Airlines group.

A judge ruled the ‘no show’ clause was unfair as there was not even a partial refund to the customer when he had intended to travel on the outbound leg on a direct flight. Spain’s Supreme Court also ruled against ‘no show’ clauses earlier this year.

Some airlines claim these practices are necessary in order to stop ‘tariff abuse’ – when passengers buy return tickets that are cheaper than a single flight.

But two of the biggest airlines in Europe – budget carriers easyJet and Ryanair – have demonstrated that it is possible to operate successfully without taking advantage of passengers in this way.

Which? has written to BA, Flybe, Virgin Atlantic, Emirates, KLM, Air France, Singapore Airlines, Qatar Airways and Swiss asking them to respond by December 28.

Which? managing director of home products and services, Alex Neill, said: “Missing a flight because you’re stuck in traffic or on a delayed train is frustrating enough, but for the airline to then turn around and say your return journey is cancelled as well is completely unfair and unjustified.

“We don’t think there’s any good reason for a ‘no show’ clause to exist – it only works in favour of the airline. It should be removed immediately by airlines, who need to show more respect for their passengers.”

A BA spokesman said: “More than 45 million customers choose to fly with us every year and we value their loyalty.

“Many of our tickets allow customers to make changes to their flights if they inform us before they travel. And if a customer arrives at the airport after genuinely missing their flight, their return flight will – of course – be protected. ​

“It is common practice within the airline industry for customers to be required to use flights in the order stated in the booking, and they are asked to agree to these terms when they make a booking.​”

A Virgin Atlantic spokeswoman said: “We are aware of the report and are in the process of investigating further. We never want to disappoint our customers and make our terms and conditions clear at the point of booking.”

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