Martin Lewishas highlighted a little-known six-year rule that means you may be entitled to compensation without realising it.

Speaking on This Morning, the money saving expert turned his forensic hand to the topic of flight compensation. While many will know that, under EU law adopted by the UK following Brexit, passengers are often entitled to financial compensation following lengthy flight delays, they may not be aware of a useful bit of small print.

"Did anyone have a flight delay or cancellation this summer? Or actually, the law says you can go back six years, except in Scotland where it is five years. So if you've had this happen to you during this time, except in certain circumstances, you are entitled to a fixed amount of compensation. £520 per person, so a family of four is over a grand, depending on the length of flight and the length of the delay and some other things," Martin told Cat Deely and Ben Shephard on Tuesday's programme.

That means it is well worth looking back at flights you may have taken as long ago as 2019 to see if any of them were delayed enough for you to claim some compensation. Online tools such as AirHelp let you check if you're owed cash for free.

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Martin went on to explain that other criteria that can determine whether you're owed compensation.

"First of all, it has to be a UK or EU-regulated flight. That is, any flight leaving the UK or European airport, that is pretty simple. Or any flight arriving to a UK or EU airport, but then it has to be a UK or EU airline. Easiest way to think of that, British Airways from New York to London is EU regulated, American Airlines from New York to London is not," he said.

"Then for a delay to count you have to have arrived, not left, three hours late. So when they open the doors of the plane.

"Cancellation rules, they have to have cancelled less than 14 days before the flight. If it's more, it's deemed that you have more time to organise. If it's less, then it depends on when the replacement flight would've landed, what you're entitled to. You'll need to look that up. There are free tools online that'll do this for you, you do not need to pay."

As many passengers have found out to their displeasure, there are certain situations in which airlines don't have to pay out despite lengthy delays or cancellations.

"The final thing is it must be the airline's fault, which is much broader than it may sound. If it is a weather issue, if it is air traffic control, if the airport shuts down, it's not the airline's fault. If it is staffing problems for the airlines, technical problems for the airlines, if it is a knock-on impact that means your flight is delayed, it is generally the airline's fault," Martin said.

When it comes to whether or not you should claim, Martin suggested the following rule of thumb.

"It's a slight moral thing. If you were three hours and one minute late, sat in the airport bar, having a great time, I wouldn't bother. We don't want airlines to go bust. If you were 12 hours late, the kids were sleeping on the floor, it was an absolute disaster, go get your money," he concluded.