Direct answer: Flight cancellations can be announced anywhere from hours to days before departure, depending on the carrier, route, and the reason for cancellation. In practice, many airlines notify passengers several hours to days in advance when a cancellation is known, but some notices happen only shortly before departure, especially for short-notice operational issues. Key points to understand

• Notification timing varies by cause
  • Controllable issues (maintenance, crew, etc.) often lead to advance notices once the issue is confirmed, sometimes many hours to days ahead for a scheduled cancellation.
  • Weather, air traffic constraints, or severe operational disruptions may result in cancellations with shorter lead times.
  • Airlines are typically required to provide status updates and rebooking options as soon as they know the cancellation is definitive, sometimes within hours of the decision.
• Regional differences
  • In the U.S., regulators require timely status updates and alternative arrangements, with carriers often sharing notices on their websites, apps, and airport displays within a standard window after a change is known.
  • In the UK and Europe, passenger rights regimes specify notification timelines and compensation in many cases, with clearer guidance on when you should be informed and what you’re entitled to when a cancellation is given with varying notice lengths.
• What you can do now
  • Check your airline’s official flight status page for the most accurate, real-time information about any planned or potential cancellation.
  • Sign up for flight alerts from the airline or use a third-party tracking service to receive notices as soon as a status changes.
  • If your flight is at risk, consider flexible options: rebooking on the same airline, seeking alternate routes, or understanding eligibility for compensation or refunds where applicable.

If you’d like, I can tailor guidance to your region (e.g., US, UK, EU) and your specific route, and help you interpret commonly cited notice windows from recent data. I can also provide a checklist for what to do if you receive a cancellation notice.