More than 900,000 passengers each year are entitled to compensation because of delayed flights, a survey has found.

The research for consumer group Which? also revealed that only four in ten of the inconvenienced customers tried to get money back from the airline.

This means consumers are missing out on millions of pounds.

If you're one of them I urge you to make a claim. Here's a quick guide to see if you are eligible.

1. It Must Be an EU Flight

It's an EU flight if you are flying with an EU-based carrier or another airline which is flying to or from an EU airport.

2. The Delay Must Be at Least 3 Hours

To claim compensation your flight must have been delayed for three hours or more.

However, there is an important rule to remember - the time is calculated when you arrive at your final destination not when you leave.

So if you're on a flight that takes off three hours late but lands two hours 30 minutes late you are not over the three-hour delay needed to be eligible for compensation.

3. The Delay Must Be the Airlin's Fault

To claim, the delay must have been due to something that was within the airline's control.

This has been subject of much debate within the courts in recent years because the airlines have tried to use this as an excuse to avoid compensation claims.

The following are within the airline's control and will not free them from liability:

 Crew shortages or other staffing problems.

 Overbooking.

 Aircraft maintenance issues.

But if the delay is due to bad weather or political unrest at your destination, these are matters clearly outside the airline's control. Volcanic activity and earthquakes are another get-out. In these circumstances you will not be successful if you try to claim compensation.

4. Time Limitation

You can apply for compensation for any delays back to February 2005. But to take an airline to court your flight must have been within the last six years in England, Wales and Northern Ireland or five years in Scotland.