Aviation collision

Impact 5
upper likelihood error bar risk indicator
lower likelihood error bar
Impact & Likelihood
Impact key
5 Catastrophic
4 Significant
3 Moderate
2 Limited
1 Minor
Likelihood key
5 >25%
4 5-25%
3 1-5%
2 0.2-1%
1 <0.2%


UK airspace and UK airlines are among the safest in the world. There has not been a fatality on a commercial passenger airline in the UK since 1989. Even with this success, the government is not complacent and is committed to maintaining and improving the high safety standards in aviation. This is done via a programmatic approach, with the Department for Transport spearheading the State Safety Programme. This involves overseeing risk management across aviation and ensuring effective safety management systems are in place across diverse organisations with a stake in aviation safety oversight to effectively mitigate risk – working closely with the Civil Aviation Authority and other key partners.


The reasonable worst-case scenario for the purposes of the assessment is based on an airborne collision involving a commercial airliner and a business jet over a major urban area as the aircraft is approaching the airport. This results in 100% fatalities of passengers and crew on board the aircraft, with further fatalities and casualties on the ground due to falling debris. Debris would also cause damage to buildings and road or rail transport in the affected area. This would require decontamination services to clean up aircraft fuel that is spread over a wide area. There would likely be closures to the airspace over the UK and the airport until the cause of the collision is established.

Key assumptions

It is assumed that measures to mitigate risks to aviation safety are broadly as effective as they were in 2018 when the last assessment was carried out. However, this assumption is tested by the Civil Aviation Authority (CAA) iteratively, and any changes to baseline effectiveness will be reflected in future updates.


Other plausible scenarios leading to an aviation crash include Controlled Flight into Terrain, pilot suicide and an uncontrolled lithium battery fire leading to a loss of aircraft. A more impactful but less likely variation could see a mid-air collision of 2 of the largest type of commercial airliners. A less-impactful variation includes the collision of 2 aircraft over a suburban or rural area, resulting in significantly lower numbers of fatalities and casualties.

Response capability requirements

A range of capabilities would be required at the local and regional level in response to the risk occurring, including local authorities and emergency services. There would be a need for decontamination services to clean up aircraft fuel. Structural engineers and builders would be needed to assess the damage from fallen debris and subsequent rebuilding of buildings and infrastructure across a wide area. The Civil Aviation Authority (CAA) and Air Accidents Investigations Branch would assess the cause of the collision and provide assurances that aircraft were safe to fly before UK airspace could be reopened. Victim support would be required for the casualties on the ground and for those in the immediate vicinity of falling debris. It may require engagement with other governments or other services (such as any non-government organisation involved in family assistance for victims of a crash) depending on the nationality of people involved.


It could take several months to clear the debris and rebuild infrastructure, with possible residential and commercial evacuations needed while repairs take place. The recovery and identification of the deceased could take months and would be complex due to the sheer scale of the collision.