Acknowledgements: The following is extracted from the UK CAA’s Airspace Infringement Working Group and can be read in full on the relevant CAA site.


An airspace infringement is the unauthorised entry of an aircraft into notified airspace. This includes flight in controlled airspace (Control Areas, Control Zones and Terminal Manoeuvring Areas), Prohibited or Restricted airspace (either permanent or temporary in establishment), active danger areas, aerodrome traffic zones (ATZ), radio mandatory zones (RMZ) or transponder mandatory zones (TMZ). 

Any airspace infringement has the potential to be a serious safety incident which may result in a mid-air collision or AIRPROX. In 2017 there were a total on 1165 airspace infringements reported, for one or more of the following reasons:

  1. The airspace infringement resulted in a loss of standard separation between air traffic and an infringing aircraft 

  2. The airspace infringement resulted in a controlling action being initiated to establish or maintain standard separation between air traffic and an infringing aircraft. This may include one or more of the following actions: 

a)   Avoiding action; 

b)   Airborne holding instructions or tactical vectors; 

c)  A cessation/suspension of planned departures or modification of a departure route. 

3. The airspace infringement was carried out in an aircraft recorded as having previously infringed. 

Where known, the pilot is contacted and asked to submit a report in the form of a pilot-initiated MOR, or by the use of the Post-infringement Questionnaire available on-line from the following link (, or via free text emails or letters. The CAA has no regulatory powers to make a pilot submit such a report, but these serve 2 purposes: 

1.    they are used in the investigation and handling of airspace infringements

2.    they are analysed to identify causal factors and trends, with a view towards reducing the number and consequences of airspace infringements. 

This report was carried out by the Causal Factor Working Group (part of the AIWG). 

Analysis and Findings 

In 2017, of the 1165 reported airspace infringements only 215 reports were received from pilots. Whilst this number is lower than desired, the Working Group (WG) found that it had sufficient data to formulate some significant findings. 


The reports were assessed against four mitigation measures that could potentially have helped to prevent or mitigate the impact of an infringement on other traffic or controllers:

1.    Use of Moving Maps with an airspace warning 

2.    Use of a Frequency Monitoring Code (FMC) or other service where FMC was not available or appropriate 

3.    Recognition of/dealing with overload, fixation and distraction 

4.    Better familiarity with aircraft and equipment

Mitigation Methods 

·       Correct use of a moving map with alert:  Possibly effective in 85% of cases

A device (e.g. Sky-Demon or other similar software) to alert the pilot that the aircraft is approaching notified airspace and that a decision is due to prevent an infringement. 

Most subject aircraft were not carrying such devices: and of those that did, in many cases the pilot apparently either did not know that the alerts were available, chose not to use them, or chose to turn the device off. However, there is evidence of pilots deliberately ignoring warnings, particularly on approach to an airfield close to controlled airspace. 

·       Using an FMC (Listening Squawk):  Possibly effective in 65% of cases

The FMC is a discrete Mode 3A SSR code that be may selected when flying in the vicinity of controlled airspace and correlates with a radio frequency that the pilot will select and monitor. Air traffic controllers may then be able to transmit warnings to an aircraft as it infringes, or even defensively prior to an aircraft infringing. FMCs are also referred to as ‘Listening Squawks’. Many pilots did not mention FMC at all in their post-infringement reports, so the WG assumed that they were not aware of it. However, a number did note that had they used it they may have avoided the infringement. Also noted on a number of occasions was pilots squawking the correct FMC, but not listening out on the correct frequency

·       Recognition of dealing with overload, fixation and distraction:  Possibly effective in 43% of cases. 

Several instances were related to passenger distraction, often with low-hour pilots. In addition, the time spent looking for landmarks nominated by passengers emerged on several occasions. Other distractions included weather, equipment and aircraft failure, communications failures and cockpit workload. 

·       Better familiarity with aircraft and equipment: Possibly effective in 24% of cases.

A lack of familiarity with the aircraft or equipment led to problems ranging from being surprised by climb performance leading to vertical infringements, to not using equipment installed (e.g. GPS) because the pilot was not familiar with its operation. 

The four mitigation measures may have helped prevent the vast majority of the occurrences reviewed. None of the measures are new to General Aviation flying activity, but it is apparent that the pilots involved were not making the best use of them. 


The majority of pilots in the reports made genuine mistakes, rather than had a poor approach to their responsibilities. However, there were a few reports of pilots knowingly infringing to avoid other risks, such as traffic warnings or deteriorating weather; this could suggest a lack of airmanship.  There were some navigation errors, such as mistaking a waypoint or setting up an incorrect heading. These were often associated with low-hours pilots. There were some instances of incorrect altimeter setting by not entering the correct pressures (e.g. Using RPS or Standard Pressure when beneath controlled airspace, and continuing en-route with QFE set). 

Most pilots had planned their flight thoroughly, but many infringements took place in the pilot’s local area. There were infringements as a result of the pilot not noticing a piece of airspace, usually a small fillet, or the vertical extent, during the planning stage. Some pilots misread charts in complex airspace, with some criticism of labelling. 

There were several instances where the pilot had not allowed sufficient margin between their planned /actual flight path and the boundary of controlled airspace. In these cases, a small vertical or horizontal error led to the infringement. A similar cause was aircraft not allowing sufficient time to descend when planning to fly under a CTA from a higher cruising level. 


All pilots will have a captaincy capacity limit. The actual limit will vary from person to person, but if a pilot recognises there is a limit and takes measures to stay within it then the instances of infringement due to overload should reduce. For example, a low-hour pilot taking a passenger for the first time should plan to fly further away from controlled airspace so that if, as in several instances, the passenger is unwell and/or causes a distraction, any resulting inaccuracy in flight is less likely to lead to an airspace infringement. Training in Human Factors, both at ab initio and recurrent level could, and should, be improved. 

Training and Preparation 

Pilots should be completely conversant with the use of any equipment in the aircraft. If the aircraft is flown under ‘self-hire’, it must be recognised that time spent on the ground understanding the equipment will help to get the most benefit from it and reduce distraction in the air.  

Flight Planning 

The two flight planning improvements that would have made the most difference are: 

  1. Planning to stay a safe distance from controlled airspace so that an inflight inaccuracy won’t lead to an infringement. (Take Two) 

  2. Planning to change levels well ahead of the airspace boundary to avoid infringing during a climb or descent. 


Pilots should take the help available by: 

  1. Making use of FMCs to make the aircraft visible and contactable by ATC; pilots of non-transponder equipped aircraft should also be encouraged to monitor the relevant frequency if an air traffic service is not required as ATC may transmit to pilots of unknown non-squawking aircraft. 

  2. Communicating with ATC where there is no FMC 

  3. Listening out at all times for help from ATC.  

                FLY SAFE!

Tony Birth