Learn when final-approach separation is 3 NM, when 2.5 NM is allowed, and how wake turbulence, runway occupancy and ATC rules increase it.
In real-world aviation, there is no single worldwide minimum aircraft separation on final approach. Under radar control, 3 NM is a common terminal minimum; approved arrival streams may use 2.5 NM near the runway. Elsewhere, 5 NM may apply, while wake turbulence, runway occupancy and local procedures can require more.
Is final-approach separation 3 NM or 2.5 NM?
Both figures can be correct, but only under the procedure that authorises them. Under ICAO surveillance procedures, the standard horizontal minimum is normally 5 NM, although the responsible authority may reduce it to 3 NM where surveillance accuracy and operating conditions permit.
A further reduction to 2.5 NM can be authorised between successive aircraft established on the same final approach track close to the runway, commonly within 10 NM of the threshold. It depends on conditions such as approach monitoring, compatible aircraft speeds, runway occupancy and suitable exits. It is unavailable when a larger wake-turbulence minimum applies.
The mistake we see constantly is treating 3 NM as a universal target. It is an ATC minimum for particular circumstances, not a distance every pilot should attempt to maintain. Controllers usually build additional margin into the arrival stream because a faster following aircraft continues closing the gap. Our explanation of how ATC sequences and separates arrivals covers that process in simulator terms.
What can increase separation on final?
The controlling separation is whichever applicable rule demands the largest gap.
- Wake turbulence: A smaller aircraft following a heavier aircraft may require substantially more than the basic radar minimum.
- Runway occupancy: The leading aircraft must normally clear the runway before the following aircraft crosses the threshold, subject to any specifically authorised reduced runway-separation procedure.
- Non-radar operations: Procedural separation may use position reports, estimated times or other criteria rather than a distance displayed on radar.
- Closing speed: Three miles with equal groundspeeds remains three miles. A fast jet following slower traffic can consume that margin rapidly, which is why ATC uses speed restrictions and vectors.
- Parallel approaches: Aircraft flying authorised independent approaches to parallel runways follow separate parallel-runway criteria. The same-stream 3 NM figure is not necessarily a lateral buffer between them.
How does wake turbulence change final-approach separation?
Wake turbulence can override a smaller radar minimum and become the controlling distance. Under the conventional ICAO HEAVY, MEDIUM and LIGHT categories, examples include 5 NM for a MEDIUM aircraft behind a HEAVY, 6 NM for a LIGHT behind a HEAVY, and 5 NM for a LIGHT behind a MEDIUM.
Some authorities and airports use more detailed wake-category or aircraft-specific systems, so the exact requirement can differ. When landing behind a larger aircraft, avoid descending below its approach path and plan to touch down beyond its touchdown point if runway length and conditions permit. If that cannot be done safely, request more spacing or go around.
How much time do 2.5 or 3 NM provide?
The distance in nautical miles becomes a time gap only after the aircraft's groundspeed is known. The calculation is distance in NM ÷ groundspeed in knots × 3600.
| Distance | At 120 kt groundspeed | At 140 kt groundspeed |
|---|---|---|
| 2.5 NM | 75 seconds | 64 seconds |
| 3 NM | 90 seconds | 77 seconds |
| 5 NM | 150 seconds | 129 seconds |
| 6 NM | 180 seconds | 154 seconds |
These figures are rounded and use groundspeed, not indicated airspeed. Wind therefore changes the time available even when both aircraft fly the same indicated approach speed. If speed control is causing an unstable approach, use our practical guidance on managing speed for approach and landing.
Who maintains separation on a visual approach?
Responsibility depends on the airspace, clearance and whether the pilot has accepted visual separation under the applicable rules. In some controlled operations, a pilot who reports the preceding aircraft in sight and is instructed to follow it assumes responsibility for maintaining visual separation and avoiding its wake.
At a non-towered aerodrome, the 3 NM radar figure is not a pilot-applied circuit rule. Pilots must sequence themselves safely, account for wake and avoid landing while the runway is unavailable. Our guide to spacing the circuit and turning final safely explains the practical cues.
What should you do if the gap becomes too small?
If the spacing no longer looks safe, request more room early and go around rather than trying to rescue a compressed approach.
- Monitor the closure rate. Look beyond the displayed distance: compare groundspeeds and consider how quickly the leading aircraft can vacate the runway.
- Tell ATC promptly. Request reduced speed, vectors or additional spacing. Do not make unapproved S-turns on final or slow abruptly below a safe stabilised speed.
- Reject unsafe wake spacing. Tell ATC if you cannot accept the spacing behind heavier traffic; a clearance does not remove the pilot's responsibility to avoid an unsafe situation.
- Go around when required. Discontinue the approach if the runway remains occupied, the aircraft becomes unstable, wake avoidance is doubtful or the landing clearance is absent.
In a flight simulator, built-in ATC or AI traffic may occasionally produce spacing that a real controller would correct. Do not force the landing through traffic. The useful rule is simple: 3 NM is a common radar minimum, 2.5 NM is a conditional reduced minimum, and the actual requirement is always the largest applicable surveillance, wake-turbulence, runway or local-procedure minimum.