NOTAMs: the advisories that can close runways and ground flights

Notices to Airmen, known as NOTAMs, are safety advisories issued to pilots and dispatchers rather than to passengers. They carry time-sensitive information that can ground an aircraft, close a runway, or change how a flight is flown.

The notices cover a range of conditions. These include active runway closures, restrictions on high-altitude military airspace, and disruptions to GPS signals. Pilots and dispatchers work through a continuous flow of such advisories.

The effect shows up in day-to-day operations. Flights change course, delay pushback, or enter holding patterns because of these restrictions. The boundaries they describe do not appear on standard flight boards, so passengers waiting at gates often see only a delay notice with no explanation of what prompted it.

For crews, the information can arrive at short notice. An advisory may require an aircraft to stay on the ground, or turn a routine approach into a more complex manoeuvre.