To file a claim for a delayed flight in 2026, you should first identify which passenger rights law applies: EC 261 (EU), UK 261 (UK), or the newly strengthened DOT rules (USA). If your flight was delayed over 3 hours for reasons within the airline's control (like mechanical issues or crew scheduling), you are often entitled to cash compensation. Start by visiting the airline's official website and searching for "Claims" or "Compensation Form." You will need your flight number, booking reference (PNR), and the length of the delay. In the U.S., the 2026 DOT guidelines now mandate automatic cash refunds if a flight is significantly delayed (over 3 hours domestic, 6 hours international) and you choose not to travel. For EU/UK flights, if the airline rejects your claim, you can escalate it to an Alternative Dispute Resolution (ADR) body or the Civil Aviation Authority (CAA). Always keep copies of your boarding passes and any expense receipts for food or hotels during the delay.