Yes, an airline will give you full flight delay refund or cancellation refund under EC 261. But the reason of disruption, delay or cancellation would also be taken in consideration. Moreover, the policies and terms & conditions may vary airline to airline. For better references, you must check and read carefully the cancellation & refund policies of determining airline. For instance, if taking in consideration JetBlue Airlines refund policies, it says that- you have the right to get a complete refund, only if you cancel the flight within 24 hours of booking. And for a JetBlue change, their 24-hours risk-free policy will save you from incurring and cancellation charges. JetBlue Airline cancellation policy depends on their different classes allotted, so read and know about them thoroughly. If in case, you are unable to understand any condition or technical jargon, then JetBlue airline customer service is available 24*7. You can call them toll-free at 00 1801-449-2525 or mail any enquiry at DearJetBlue@jetblue.com.