You can now claim compensation for delayed flights and other types of claim under EC Regulation 261/2004 up to 6 years from the date of travel, so ruled the Court of Appeal ruled on 19-06-14. Thomson Airlines tried to argue that the correct period was 2 years under the Montreal Convention but this was rejected.
If you have had a claim rejected by the airline because it is more than 2 years old try again! and mention the case of Dawson v Thomson Airlines – Court of Appeal 2014. If you have been to court and had a claim dismissed then you may be able to appeal if you are within 21 days of the decision otherwise you are probably stuck with that decision.