EU Flight delay compensation - quick guide

EU Rules EU Regulation 261/2004.

If your flight has been delayed by at least three hours (delay must be arrival time not departure time, e.g. the aircraft could depart 3.5hrs late and arrive 2hrs 59 mins late) or cancelled then you have the right to compensation under European law. Under EU Regulation 261/2004, passengers are entitled to up to €600 Euros (GB£530) in compensation 

the amounts available start from €250 (GB£221) for flights of less than 1,500km long which are delayed by at least three hours and go up to €600 (GB£530) for flights of more than 3,500km between an EU and non-EU airport, delayed by at least four hours.

Under the EU rules, an airline must pay compensation for cancelled or delayed flights, The flight must have departed from an EU airport, operating by any airline, or it must be arriving into an EU airport and be operated by an EU airline. The 'EU airport' also includes the following countries;, Liechtenstein, Iceland, Switzerland and Norway 

There has been some legal clarification regarding the rules recently in the UK two  Supreme Court rulings declared that carriers should pay out when a delay was caused by a technical fault.

Here is the link to the EU page  http://europa.eu/youreurope/citizens/travel/passenger-rights/air/index_en.htm