The FAA defines a runway incursion as any occurrence at an airport involving the incorrect presence of an aircraft, vehicle or person on the protected area of a surface used for landing and take-off. Most are minor. The ones that end in collisions usually happen in poor visibility, at busy or confusing airports, when a pilot or controller believes the runway is clear and it is not. The deadliest was at Tenerife in 1977.
What counts as a runway incursion
The definition covers any aircraft, vehicle or person that is wrongly on a runway, whether or not anything else is near it. The FAA grades each incursion by how close it came to a collision:
| Category | FAA definition |
|---|---|
| A | A serious incident in which a collision was narrowly avoided |
| B | Separation decreases and there is a significant potential for collision, which may need a time-critical corrective or evasive response |
| C | There was ample time or distance to avoid a collision |
| D | An aircraft, vehicle or person was wrongly on the protected area, but with no immediate safety consequences |
Category A and B events are what people usually mean by a runway near miss. The FAA also sorts incursions by who caused them. Operational incidents are caused by an air traffic controller’s action, such as clearing an aircraft onto a runway that is occupied or closed. Pilot deviations are caused by a pilot breaking a rule, such as crossing a runway without clearance. Vehicle or pedestrian deviations are when someone drives or walks onto the movement area without permission.
Incursion vs excursion
The two words sound alike but describe different events. An incursion is about something being on the runway that should not be there. A runway excursion is, in the ICAO wording the FAA uses, “a veer off or overrun from the runway surface”: an aircraft that leaves the runway during take-off or landing. A collision with another aircraft is an incursion. Sliding off the end after a fast landing is an excursion.
Tenerife: the deadliest
On 27 March 1977 two Boeing 747s collided on the runway at Los Rodeos Airport on Tenerife. The full account is on the Tenerife airport disaster page. This section is about the runway itself.
A runway used as a taxiway. A bomb at Las Palmas had sent dozens of flights to Los Rodeos, a small airport with one runway. Parked aircraft filled the parallel taxiway. To reach the take-off position, departing aircraft had to taxi down the runway and turn around at the end, which is called backtracking. KLM Flight 4805 backtracked first. Pan Am Flight 1736 was told to follow it and leave the runway at the third exit, C3. Low cloud rolled across the airfield, and the FAA’s summary records that visibility dropped until some aircraft were no longer visible from the tower. The tower had no ground radar.
Two aircraft on one runway. At the end of the runway, the KLM 747 turned around and began its take-off roll without a take-off clearance. At 17:06:09, while reading back his route clearance, the KLM first officer added “we’re now (at takeoff)”. The tower replied “okay”, then “stand by for takeoff, I will call you”. At the same moment the Pan Am crew reported that they were still taxiing down the runway. The two transmissions blocked each other, and the KLM crew heard neither clearly. The Pan Am aircraft had not left at C3. The FAA’s summary says its crew may have assumed, because of how the airport was laid out, that the controller meant a later exit.
The toll. All 248 people on the KLM aircraft and 335 on the Pan Am aircraft were killed, a total of 583. Sixty-one people on the Pan Am aircraft survived. The Spanish board found the fundamental cause was the KLM captain’s decision to take off without clearance.
Both aircraft were Boeing 747s. The cockpit and radio lessons, including the change to how the word “takeoff” is used, are covered in What Changed After Tenerife. The FAA says Tenerife was, in part, behind its “Call to Action” on runway safety in August 2007.
Other runway collisions
These accidents do not have event pages on this site yet.
- Detroit, 3 December 1990. In fog, a Northwest Airlines DC-9 (Flight 1482) got lost while taxiing and entered the active runway. A Northwest Boeing 727 (Flight 299) on its take-off roll struck it. Eight people on the DC-9 were killed, and nobody on the 727 was hurt. The NTSB found the probable cause was a lack of proper crew coordination, including what it called a virtual reversal of roles between the DC-9’s pilots. That led to their failure to stop taxiing and tell the ground controller they were unsure of their position. Air traffic control deficiencies contributed, among them the failure to use progressive taxi instructions in low visibility.
- Los Angeles, 1 February 1991. USAir Flight 1493, a Boeing 737, was cleared to land on a runway where SkyWest Flight 5569, a Fairchild Metroliner, was holding in position. Twelve people on the Metroliner and 22 on the 737 were killed. The NTSB found the probable cause was the failure of the Los Angeles tower’s management to put in place procedures that gave enough redundancy, and the failure of the FAA to give adequate direction and oversight. That environment ultimately led the local controller to lose track of the traffic and issue the conflicting clearances.
- Milan Linate, 8 October 2001. In fog, a Cessna 525-A business jet that had been cleared to taxi via taxiway R5 followed R6 instead and entered the active runway. A Scandinavian Airlines MD-87 (Flight 686) taking off struck it. Everyone on both aircraft and four ground staff in a baggage building were killed. Italy’s ANSV found the immediate cause was the Cessna’s runway incursion. It also found that the airport’s systems were “not geared to trap misunderstandings”: signage and markings that did not identify the route, and no working surface movement radar since November 1999.
None of these collisions came down to one person, which is why investigators look at the whole chain, as the Swiss cheese model describes.
What changed
- Clear radio words. After Tenerife, controllers use the word “takeoff” only when they give or cancel a take-off clearance, and “departure” at other times. The Detroit report also faulted the DC-9 crew for not stopping and telling the ground controller as soon as they were unsure where they were.
- Stop bars and markings. Runway holding position markings tell pilots where to stop before a runway, and some airports add red stop bar lights. At Linate the Cessna crossed a holding marking on a route it should not have been on. ANSV found that the airport’s signs and markings did not let the crew identify where they were.
- Surface radar. ASDE-X combines radar, multilateration sensors and ADS-B to track aircraft and vehicles on the airport surface, including those without transponders. It sounds visual and aural alarms to warn controllers of a possible runway incursion. The FAA lists 35 major US airports with it.
- Runway status lights. The FAA’s runway status lights are set into the pavement. They turn red automatically when it is unsafe to enter or cross a runway (runway entrance lights) or to begin a take-off (take-off hold lights), with no input needed from controllers. The FAA says they are working at 20 US airports.
Collision warnings in the air followed a similar path; see TCAS and Terrain Warnings. To read the investigators’ reasoning in full, How to Read an Air Accident Final Report explains how the reports are laid out.
Four runway collisions compared
| Collision | Date | Conditions | What was on the runway | Deaths | Investigating body |
|---|---|---|---|---|---|
| Tenerife: KLM 4805 and Pan Am 1736 | 27 March 1977 | Fog, congested airport, no ground radar | Pan Am 747 still taxiing on the runway | 583 | Spain (Subsecretaría de Aviación Civil) |
| Detroit: Northwest 1482 and 299 | 3 December 1990 | Fog | Lost DC-9 taxied onto the active runway | 8 | NTSB |
| Los Angeles: USAir 1493 and SkyWest 5569 | 1 February 1991 | After dark (18:07 local) | Metroliner holding in position, landing 737 cleared onto it | 34 | NTSB |
| Milan Linate: SAS 686 and Cessna D-IEVX | 8 October 2001 | Fog, no surface radar | Cessna on the wrong taxiway entered the runway | All on both aircraft and 4 on the ground | ANSV (Italy) |
Sources
- Federal Aviation Administration: Runway Incursions (definition, categories A to D, sources of incursions)
- Federal Aviation Administration: Runway Excursions
- Federal Aviation Administration: Lessons Learned: KLM Flight 4805 and Pan Am Flight 1736, Tenerife, March 27, 1977 (with the Spanish board’s findings)
- Agenzia Nazionale per la Sicurezza del Volo (ANSV), Italy: Final Report A/1/04, accident at Milano Linate airport, Boeing MD-87 SE-DMA and Cessna 525-A D-IEVX, 8 October 2001 (approved 20 January 2004)
- National Transportation Safety Board: Aircraft Accident Report NTSB/AAR-91/08, Runway Collision of USAir Flight 1493 and SkyWest Flight 5569, Los Angeles International Airport, February 1, 1991
- National Transportation Safety Board: Aircraft Accident Report NTSB/AAR-91/05, Northwest Airlines Flights 1482 and 299, Runway Incursion and Collision, Detroit Metropolitan/Wayne County Airport, December 3, 1990
- Federal Aviation Administration: Runway Status Lights (RWSL)
- Federal Aviation Administration: Airport Surface Detection Equipment, Model X (ASDE-X)
Last checked 31 October 2026.