Drone Incident and Airprox Reporting in the UK

What Is an Airprox?

An airprox (air proximity hazard) is a situation in which, in the opinion of a pilot or air traffic controller, the distance between aircraft — including unmanned aircraft — was such that the safety of the aircraft involved may have been compromised. Airprox events are the aviation equivalent of road traffic near-misses.

The term applies regardless of whether a collision actually occurred. The defining factor is whether the separation between the aircraft was sufficient to maintain safety.

The UK Airprox Board (UKAB)

The UK Airprox Board is an independent body that receives, investigates, and categorises airprox reports. It is jointly sponsored by the CAA, the Ministry of Defence, and NATS (the UK's air navigation service provider). The UKAB does not have enforcement or prosecutorial powers — its role is to investigate, assess risk, and publish findings to improve aviation safety.

UKAB Risk Categories

After investigating an airprox, the UKAB assigns one of five risk categories:

• Category A: risk of collision. Aircraft were in such proximity that a serious risk of collision existed.
• Category B: safety not assured. The safety of the aircraft was compromised.
• Category C: no risk of collision. Despite the proximity, no risk of collision existed in the circumstances.
• Category D: risk not determined. Insufficient information was available to make a risk assessment.
• Category E: normal encounter. The proximity was within the bounds of normal operations.

Drone-related airprox reports have increased significantly in recent years, reflecting both higher drone usage and improved reporting practices. The UKAB publishes statistics and individual case summaries on its website.

Mandatory Occurrence Reporting (MOR)

Under Regulation (EU) 2015/1018 as retained in UK law and the CAA's implementing requirements, certain aviation occurrences must be reported to the CAA. This is known as Mandatory Occurrence Reporting (MOR).

Who Must Report

The obligation to file an MOR applies to:

• Holders of CAA operational authorisations (such as those operating under an Operational Authorisation for specific categories)
• Pilots of manned aircraft who observe a drone-related occurrence
• Air traffic controllers who become aware of a drone incursion

Recreational drone operators who do not hold a CAA operational authorisation are not strictly required to file an MOR, but voluntary reporting is strongly encouraged and helps improve safety data.

What Must Be Reported

Reportable occurrences include:

• Any airprox involving an unmanned aircraft
• Loss of control of an unmanned aircraft
• Unintended entry into controlled airspace or a restricted zone
• Injury to any person caused by the drone or its operation
• Significant damage to property
• Any event that could have resulted in an accident

How to File an MOR

Reports are submitted to the CAA through the online occurrence reporting portal. The report should include details of the date, time, location, aircraft involved, weather conditions, and a factual description of the event. Reports should be filed as soon as practicable — normally within 72 hours of the occurrence.

Voluntary and Confidential Reporting

The CAA operates a Confidential Human Factors Incident Reporting Programme (CHIRP) alongside the mandatory system. CHIRP allows anyone — including recreational drone operators — to report safety concerns confidentially. Reports submitted through CHIRP are anonymised and used to identify safety trends without exposing the reporter to enforcement action.

Additionally, airprox reports can be filed directly with the UKAB by any party involved in or witnessing an airprox event.

Does Reporting Mean You Will Be Prosecuted?

Filing an occurrence report — whether mandatory or voluntary — is not an admission of fault and does not automatically lead to enforcement action. The UK aviation safety reporting culture is built on the principle that honest reporting improves safety for everyone. The CAA has stated that it will not normally take enforcement action against operators who voluntarily report occurrences, provided the report is not made to pre-empt enforcement action the reporter knew was already underway.

That said, the information in a report may be used alongside other evidence if a separate investigation identifies criminal conduct. The report itself, however, is treated as a safety document, not a confession.

What Happens After a Report Is Filed

1. Initial assessment: the CAA or UKAB reviews the report to determine its seriousness and the appropriate level of investigation
2. Investigation: for significant events, investigators may contact the reporter and other parties for additional information
3. Classification: the UKAB assigns a risk category (for airprox events)
4. Publication: the UKAB publishes anonymised summaries of investigated airprox events in its regular reports
5. Safety action: where systemic issues are identified, the CAA may issue safety notices, amend guidance, or recommend regulatory changes