More passengers could be able to successfully claim compensation for flight delays, after new guidelines were issued by European regulators.

Importantly the new guidelines mean that if there is a technical fault, in many cases airlines will no longer be able to use this as a reason to wriggle out of paying compensation for delays.

Any complaint that's currently with the CAA but which hasn't been assessed by it will also be sent back to the original airline to look into again using the guidelines.

EU rules say passengers whose flights are significantly delayed can, in certain circumstances, claim up to €600 (£516) per person, dating back to 2005. See our Flight Delays guide for how to do this, as well as information on your rights when a flight is cancelled.

This only applies if the delay is the airline's fault. If it isn't, which is known as an "extraordinary circumstance", then customers have no right to redress.

But now new guidelines have been hammered out after talks between European regulators, technical experts and the airline industry.

When you won't get compensation

What counts as an extraordinary circumstance is sometimes a grey area.

Previously the only information given on when a  delay wasn't an airline's fault were the following general issues: bad weather, industrial action, political problems and security or safety issues and air traffic management decisions.

But the new guidelines say an "extraordinary circumstance" has to meet three criteria: unpredictable, unavoidable and external.

There's also a specific list of 30 examples of what is "likely" to be considered an extraordinary circumstance, along with five examples of when a delay is likely to be an airline's fault. See the European Commission (EC) website for the full list.

The guidelines have been created by individual European regulators. The EC, which enforces EU law, says the list isn't an exhaustive one and could change in future.

Technical issues

Importantly, the new guidelines clarify that some technical issues, which airlines often claim are out of their control, are in fact likely to be the airline's fault – meaning consumers could be eligible for compensation in these circumstances.

If the airline discovers "a hidden manufacturing defect" on the aeroplane, then that counts as an extraordinary circumstance.

But technical issues "found during maintenance where the part or system in question was scheduled to be checked" do not count. National regulators will scrutinise cases to see whether "distinguishing factors" exist.

Appeals to go back to the airline

As a result of the new guidelines, any complaint that's currently with the CAA but which hasn't been assessed by it will be sent back to the original airline to look into again. In newer cases the airline will then let customers know its decision.

Older cases, mostly from last year, will be sent back to the airline to reassess, and then automatically sent to the CAA to review. The CAA will get in touch with customers to let them know its decision.

Airlines have until the end of September to assess these complaints, so consumers should hear from either the CAA or the airline by then, although complaints which are being reviewed by the CAA may take slightly longer.

Could you complain again?

If you complained to the airline and had your complaint rejected, but never took your case to the CAA, it's worth looking at the new list of guidelines to see if your case was wrongly discarded, and complain again to your airline if you believe it was wrongly rejected.

However, if both the airline and the CAA have previously rejected your claim, it's unlikely you'll get that decision overturned as the CAA says it was already using guidelines similar to the new ones to assess complaints.

The European Commission says it isn't aware of regulators in other countries asking airlines to review previously rejected claims.

Passengers have been able to claim compensation for flight delays since last October, when the European Court of Justice rejected a challenge to the rules from airlines. See the Flight delay compensation floodgates open MSE News story.