EU261, formally known as Regulation (EC) No 261/2004, is a European Union law that outlines the rights of air passengers in cases of flight disruptions. These disruptions can include delays, cancellations, or denied boarding. The key point here is that these disruptions must be within the airline's control to fall under the regulation. Now, when it comes to eligibility, EU261 applies to all flights departing from an EU airport or arriving at an EU airport with an EU-based airline so look these up. This broad scope covers a significant number of flights and ensures a wide range of passengers can benefit from these rights. For those interested in delving deeper, it's advisable to read the actual text of EU261. You can easily find it online by searching for "EU261 regulation." This document provides the official and comprehensive details of the regulation, offering a clear understanding of passenger rights and the responsibilities of airlines.