To stop people buying return flights that were cheaper than singles, many airlines have put controversial "no show" clauses in their contracts.
The loophole people were exploiting came about from the way airlines price flights. For example, while there is high demand in the summer months to fly from Newcastle to Barcelona, the reverse isn't always the case.
That meant it could be cheaper to book a return from Barcelona to Newcastle, and only use the second leg of the flight, than a one-way fare.
As a response, many airlines put clauses in their contracts that meant the return leg of a journey was automatically cancelled if you didn't get on the first trip.
But entirely honest passengers can end up paying the price of this - because now if for any reason you miss the outbound leg of your flight you could be forced to buy an entirely new, one-way ticket to get home.
That means paying prices for anything left available on the day - although sometimes they let you use your original tickets if you pay a fee. The downside is that the fee can be more than £2,000.
Worse, the first you hear of it could be at the terminal - as was the case with Sara Montgomery, who the Daily Record spoke to when it happened to her .
Sara from Bellshill said: "At no point did we think they would cancel our return flight."
She added: "They told us they had cancelled our return leg of the journey as we failed to show up for the first ... We ended up having to buy tickets for our plane we thought we already had seats for - at £330 each."
Not all airlines have this clause - for example, easyJet, and Ryanair don't impose these rules on passengers.
With them, you buy two separate flights, so if you miss one it doesn't affect the other journey you have booked. Thomas Cook has also scrapped the clause.
But it's something you'll need to be very careful about, or risk a delay getting to your outbound flight resulting in a huge extra expense.
Alex Neill from Which? 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."
Airlines warned 'no show' clauses could be breaking consumer laws
The good news is that in some cases you might be able to fight the charge and win.
For example, back in 2017 a passenger won compensation from airline Iberia after a judge ruled the clause was unfair as there was no refund given to the customer who had intended to travel.
But to be on the safe side, it might be worth checking the terms and conditions very carefully when you next book a return ticket.
Thankfully, there is a small bit of good news.
If you miss your flight you can still reclaim your Air Passenger Duty - that’s the tax all travellers pay to fly from the UK - which could be worth as much as £528 in some cases.
