What are NOTAMs, and how do they affect ATC and flight planning?
What are NOTAMs? Learn how they change ATC clearances and flight plans, and how pilots catch closures, outages and airspace restrictions.
In real-world aviation, NOTAMs are time-critical operational notices about changes or hazards that may affect a flight, such as closed runways, unserviceable navigation aids, procedure amendments or airspace restrictions. Pilots and dispatchers use them to plan safely; air traffic control uses relevant NOTAM information when assigning routes, runways, altitudes and clearances.
In the United States, the FAA expands NOTAM as Notice to Air Missions; older material and some jurisdictions use Notice to Airmen. We treat a NOTAM as an operational update to the published aeronautical picture, not as a substitute for charts, weather reports or permanent airport information.
What information is in a NOTAM?
A NOTAM identifies the affected location or facility, the nature of the change, its effective period and, where relevant, its altitude or geographical limits. Notices cover temporary conditions and operationally significant permanent changes that cannot wait for the next publication cycle.
Typical subjects include:
- Runway or taxiway closures, shortened declared distances and construction work.
- Unserviceable approach lighting, communications equipment, navigation aids or instrument procedures.
- Temporary flight restrictions, danger areas and other airspace limitations.
- New obstacles, cranes, hazards and changes to airport operating arrangements.
- Amendments to routes, departure procedures, arrival procedures and approach minima.
At US airports, permanent baseline data comes from the Chart Supplement, while NOTAMs describe later operational changes. Our explanation of reading airport entries alongside current notices shows why both sources are needed.
Categories and formats vary by state. FAA FDC NOTAMs commonly carry regulatory information, including procedure amendments and temporary flight restrictions, while NOTAM (D) messages generally concern airports and facilities. International messages may use NOTAMN for a new notice, NOTAMR for a replacement and NOTAMC for a cancellation. The category does not indicate how serious the operational effect will be.
| NOTAM subject | Flight-planning effect | Likely ATC effect |
|---|---|---|
| Runway or taxiway closed | Recalculate performance and check whether another surface is suitable | Different runway, taxi route, holding instructions or delays |
| ILS, NAVAID or procedure unavailable | Select another approach and reconsider fuel or alternate requirements | Vectors, a different procedure or suspension of the affected approach |
| Temporary airspace restriction | Change route, altitude or departure time | Rerouting, flow restrictions or refusal of entry |
| Lighting or communications outage | Assess night, IFR and equipment requirements | Alternative communication arrangements or restricted runway use |
| Obstacle or work in progress | Check performance, operating limits and applicable procedures | Changed runway configuration, taxi instructions or local restrictions |
NOTAM effects on air traffic control
ATC uses operationally relevant NOTAMs to configure the airport, suspend unavailable procedures, protect closed surfaces and route aircraft around active restrictions. A closure or outage can also reduce airport capacity, leading to spacing, holding, reroutes or ground delays even when the flight itself remains legal.
For example, controllers will not normally clear an aircraft to use a closed runway, and an approach cannot be assigned if a controlling navigation aid or procedure has been withdrawn. A published departure that becomes unavailable may result in an amended clearance or radar vectors. These changes fit into the wider clearance and ATC coordination sequence from departure to landing.
An ATC clearance does not make an unsuitable airport, unavailable procedure or prohibited airspace acceptable. The pilot in command must determine whether the clearance can be accepted, and an ordinary clearance must not be treated as automatic permission to enter airspace restricted by a controlling NOTAM.
Will ATC tell pilots about every NOTAM?
No. ATC may broadcast or advise significant local information, but pilots should not expect controllers or the ATIS to provide a complete NOTAM briefing. Notices affecting an alternate, an en-route facility, a destination approach or a future validity period may never be read over the radio.
If a notice makes the planned route or procedure unusable, tell ATC and request an amendment. Ambiguous wording should be resolved through an authorised briefing source before departure rather than assuming a controller will correct the plan later.
How NOTAMs change flight planning
NOTAMs can make a planned flight illegal, impractical or simply less efficient. Their effect depends on the aircraft, expected weather, operating rules and the alternatives available at the notice’s effective time.
- Airport suitability: A closed or shortened runway can invalidate take-off or landing performance calculations.
- Approach availability: An ILS outage may be manageable in good visual conditions but decisive when the forecast requires that approach or when it affects alternate planning.
- Route availability: A closed airway, amended procedure or temporary restriction may require extra track miles and fuel.
- Timing: Delaying departure may avoid a closure or restriction, but only if the stated validity period and time zone have been interpreted correctly.
- Contingency planning: A destination limitation may require a different alternate, additional holding fuel or a more conservative diversion point.
Airline dispatchers incorporate these effects into routes, fuel loads, alternates and operational releases. Our overview of how dispatchers turn operational constraints into release decisions explains that shared planning role.
How should pilots check NOTAMs before flight?
Pilots should obtain a fresh briefing from an official source, review every location and time relevant to the flight, then convert each significant notice into a specific planning decision.
- Search the complete operation. Include the departure, destination, alternates, route corridor, relevant airspace and any procedure or navigation aid the flight may use. An airport-only search is not enough.
- Match the validity period to the flight. NOTAM times are normally expressed in UTC. Check whether the notice will be active at departure, en route and at the estimated arrival time, not merely when the briefing is retrieved.
- Decode its scope. Confirm the airport or facility identifier, runway direction, coordinates, radius and lower and upper limits. For US restrictions, verify the TFR’s effective times, altitude limits and mapped boundaries.
- Classify the operational effect. A closure or prohibition normally demands a route, runway or timing change. An equipment outage requires a check for an approved substitute. Advisory information may require only a briefing and monitoring.
- Update the plan and brief the crew. Recalculate performance and fuel, change the alternate or route where necessary, and identify any amended communication or taxi procedure.
- Recheck before departure. NOTAMs can be issued, replaced or cancelled after the initial briefing. Check again when a delay moves the flight into a different validity window.
Common NOTAM mistakes and fixes
The most dangerous NOTAM errors come from searching too narrowly or reading the code without checking its operational context.
- Reviewing only the destination: Include the departure, alternates, route and associated airspace or facilities.
- Trusting filters blindly: A briefing application may group or suppress categories. Review critical airport and route notices rather than relying only on a map symbol.
- Confusing UTC with local time: Convert every relevant validity window and account for a flight crossing midnight.
- Misreading runway designators:
RWY 09/27 CLSDcloses the physical runway in both directions, not just runway 09. - Assuming an estimated end means service is restored: Treatment of estimated validity varies by system. Look for a cancellation, replacement or updated briefing instead of relying on the estimate.
- Using a saved briefing as live information: A downloaded or cached copy is a snapshot. Retrieve updated notices after delays or material route changes.