ACL’s Monitoring & Sanctions Process

What is misuse of a slot?

Misuse of a slot is defined by Regulation 14 of the Airports Slot Allocation Regulations 2006 (click here for a copy) as:

the repeated and intentional:

  • operation of air services at times significantly different from the allocated slots (essentially early or late operation); or
  • use of slots in a significantly different way from that indicated at the time of allocation (for example, operating a different aircraft type), where such use causes prejudice to airport or air traffic operations.

The Misuse of Slots Enforcement Code (available here) sets out more guidance on what constitutes misuse and what is meant by the terms “repeated” and “intentional”.

How do we monitor use of slots?

Slot monitoring is predominantly carried out by comparing actual slot usage (supplied by the Airports we coordinate) with allocated slots in the ACL system. Monitoring is normally carried out weekly for all ACL coordinated airports. ACL also monitors the use of slots using a variety of third party data sources (e.g. the internet). Our routine slot monitoring covers seasonal monitoring (i.e. monitoring a series of operations at any time across a season) and ad hoc monitoring (i.e. the monitoring of non-series traffic).

ACL monitors:

  • significant off slot operations (i.e. early or late operation);
  • operations in a significantly different way (e.g. operating a larger aircraft or unauthorized use of the Night Quota);
  • failure to cancel a slot which is not being operated;
  • operations without a slot.

How does ACL identify potential misuse?

We identify carriers for possible investigation either as a result of our slot monitoring activities or following a complaint (e.g. from an airport).  Any complaint received will be carefully reviewed by ACL to decide whether or not the complaint merits further investigation or action.

The majority of slot monitoring at ACL is carried out by matching actual records supplied to ACL by the Airports against the scheduled (allocated) flight in the ACL system. Discrepancies in flights operating without a coordinated slot, operating significantly off slot or operating in a significantly different way to the allocated slot are reviewed by our team who may decide to raise a query with the carrier concerned (stage 1 of the investigation process detailed below).

Seasonal monitoring of on time performance is carried out using a mathematical formula called the sig–t test, which was invented in the 1900s.  It uses objective, consistent and non-discriminatory criteria to identify operations with a 90% statistical probability of being significantly early or late.  It is able to distinguish regular (possibly intentional) off slot operations from occasional delays.

In addition to seasonal monitoring of on-time performance, we may carry out pre-season checks to identify cases of misselling (i.e. a carrier selling flights which do not accord with the slot times allocated) and to check block times for discrepancies against average block times for the same route pairs.

Investigations can be carried out before or after a flight has operated.  Investigation of flights which have already operated can start with:

  • use of the Sig-t test;
  • a complaint from a third party (e.g. an airport, another carrier, FBO or handling agent);
  • re-investigation as a result of new information.

Investigation of operations prior to the flight(s) being operated can start with:

  • website checks – to identify whether a carrier is selling contrary to the airport slots allocated;
  • use of data to identify obvious block time discrepancies – possibly in comparison to other flights on the same route;
  • checks against the EUROCONTROL Flight Plan Archive to identify flight planning contrary to confirmed times;
  • review of the ACL waitlist to identify differences between a carrier’s required and cleared times;
  • review of activity in peak hours (e.g. first wave departures).

ACL’s investigation process

Once potential misuse has been identified (see section on how we identify misuse above), we will proceed to investigate.  Investigations will normally follow a four stage process.

Stage 1 – Initial investigation

Once an operation has been flagged as potential slot misuse, the team member investigating may look at other evidence, such as:

  • previous correspondence with the carrier, for the same type of misuse or for the same flight;
  • checks against the carrier’s website to ascertain whether the flights being sold accord with the slots allocated;
  • checks against the EUROCONTROL Flight Plan Archive to ascertain whether the carrier is flight planning incorrectly;
  • use of data to identify obvious schedule / block time feasibility issues;
  • use of ACL turn reports (compiled using data we hold in our coordination system) to identify obvious lack of turn time.

The team member will review the initial evidence with their Manager. Together they will decide if a formal query should be raised with the carrier for an explanation of the potential breach of Regulation 14 of the Airports Slot Allocation Regulations 2006 or if no further action is to be taken.

If we decide to raise a formal query with the carrier, this will normally be sent in the form of an email.  It will identify the flights on which we think there may have been a breach of Regulation 14 and ask the carrier for an explanation.

It is important that carriers fully engage with ACL at this stage as this is the first opportunity for a carrier to explain the apparent off-slot operation and potentially to avoid enforcement action (by explaining why the incident was beyond the carrier’s reasonable control (which we explain here)) or explore whether a scheduling solution can be implemented to mitigate or avoid the off-slot operation.

Failure to respond to a query from ACL or to provide information which we request is an offence under the Airports Slot Allocation Regulations 2006. ACL can levy a financial sanction for this.

Stage 2 – ACL considers carrier’s response

On receipt of the response from the carrier, the team member investigating will fully review the response with their manager to agree what next steps should be taken, for example:

  • we may decide that the carrier has satisfactorily demonstrated that the cause of the breach of Regulation 14 of the Airports Slot Allocation Regulations 2006 was beyond its reasonable control. In this scenario, we would write to the carrier confirming that the case is closed and no further action will be taken;
  • we may write to the carrier requesting further clarification or to ask for further evidence or explanation on certain points. Again, it is very important that a carrier fully engages at this stage, as failure to do so may prejudice a carrier’s ability to avoid a formal sanction;
  • we may raise a query with a third party (such as an airport or ground handler);
  • we may consider that the investigation should go to stage 3 (which is explained below).

Stage 3 – Decision on whether to proceed to sanction or issue a formal warning

If the Team investigating considers that the carrier has not satisfactorily demonstrated the breach of Regulation 14 of the Airports Slot Allocation Regulations 2006 is beyond its reasonable control, the case is passed to ACL’s Slot Performance Manager.

The Slot Performance Manager will review the investigation up to that point and may decide to take one of the following actions:

  • raise further questions with the carrier;
  • close the case and take no further action (in which case the carrier will be informed in writing);
  • levy a formal sanction for the misuse, in which case we will issue a formal Notice of Proposed Decision (NPD).

Where a NPD is issued, no sanction is effective at this stage; it is simply the formal notification of the proposed sanction which we are required to give under Regulation 16 of the Airports Slot Allocation Regulations 2006.  The NPD sets out the detail of the penalty proposed (the amount of financial penalty and the basis on which it has been set) and the reasons for the penalty being proposed.  Detail of the types of sanction we can impose can be found here.

The carrier will be given up to 14 days (but less in urgent cases) to respond to the NPD.  The carrier can respond in writing or it can request an oral hearing (which will normally be held in private at ACL’s offices with the Slot Performance Manager).

Further detail on this can be found in the Misuse of Slots Enforcement Code (available here).  This is an extremely important stage as it represents the final opportunity for the carrier to query the proposed penalty and to seek to defend the alleged slots misuse.  It is therefore very important that the carrier engages with ACL at this stage if it has reasonable grounds to believe that the sanction should not be issued.

Stage 4 – Decision on whether to issue final sanction

ACL’s Slot Performance Manager will review any response to the Notice of Proposed Decision and will then decide either:

  • to close the case and take no further action (in which case the proposed sanction is cancelled);
  • to cancel the sanction and instead issue the carrier an official warning;
  • to proceed to issue a Notice of Final Decision. This is the point at which the sanction becomes formally levied and is payable by the carrier.  At this point, the carrier has no further right of challenge with ACL.  However, it does have a right to have the case assessed by an independent reviewer in certain circumstances (see “Your right to appeal” below). More information on the Notice of Final Demand can be found in the Misuse of Slots Enforcement Code (available here).

What action can ACL take for slots misuse?

When we raise a query for potential slots misuse, a formal sanction is not inevitable; ACL will thoroughly investigate the potential breach and has a number of options available to it:

  • No further actionACL can at any time prior to issuing a Notice of Final Decision, decide to stop an investigation and take no further action. We will always notify the carrier in writing of this decision and the case will then be closed.
  • Warning – ACL can at any time during its investigation decide to issue an official written warning to the carrier. This means that no sanction is applied but the carrier will be monitored to check future slot compliance.  Any further instances of slot misuse at the same airport during the period falling six months from the date of the last incident may be subject to sanction and the warning will be taken into account in setting the level of sanction.
  • Financial sanction – Regulation 16 of the Airports Slot Allocation Regulations 2006 (see here for a link to the Regulation) states that a carrier can be fined up to £20,000 on each instance of slot misuse. Section 6.2 of the Misuse of Slots Enforcement Code sets out the criteria we will consider when setting the level and type of sanction.
  • Direction – we can issue a direction under Regulation 15 of the Airports Slot Allocation Regulations 2006 for the purpose of securing compliance with the duty set out in Regulation 14.
  • Withdrawal of slots – Article 14 of the EU Slot Regulation (transposed into English law on 1 January 2021) allows ACL to withdraw slots from a carrier in certain situations.

Incidents beyond a carrier’s reasonable control

Regulation 16(4) of the Airports Slot Allocation Regulations 2006 (available here) covers the possibility of potential misuse of slots which is beyond a carrier’s reasonable control. We set out some guidance in the Misuse of Slots Enforcement Code (available here) on this.

An important point to note is that the Regulation places the burden of proof on the carrier.  This means that the carrier must reasonably demonstrate to ACL (on a balance of probabilities) that the cause of the slots misuse was beyond its reasonable control.

The Code provides some examples of the type of misuse that can be considered beyond the reasonable control of the carrier.  However these examples are not exhaustive nor will they always be sufficient as ACL has to consider the particular circumstances of each case. The carrier will need to explain how the circumstances relied on were outside of its reasonable control and how they caused the breach of Regulation 14. We may ask the carrier for data or documents to substantiate that explanation.

Carrier’s right to appeal

When we issue a financial sanction, we must first give you notice of the sanction proposed and state our grounds for levying it.  We do that by sending you a Notice of Proposed Decision (NPD).  When you receive a NPD, you have the right to submit to us any reasons why you think the imposition of a sanction is not justifiable.  Normally, you must do that within fourteen days of the date of the NPD.

It is very important that you engage with ACL at this stage if you think you have grounds to challenge the proposed sanction, as failure to engage with us can prejudice the strength of any challenge through independent review at a later stage.  In addition, at this stage no sanction is actually applied so it is your last opportunity to seek to defend the slots misuse and to avoid a sanction.

If you respond to a NPD, ACL’s Slot Performance Manager will carefully consider any evidence you submit and review it with ACL’s Head of Regulatory Affairs or the Head of Coordination.  If we feel that a sanction is still justified, we will send you a Notice of Final Decision (NFD) and it is at this stage that a fine is payable.

The process for appeal after the NFD is issued, is for the carrier to request an independent review.  The independent reviewer is fully independent of ACL and has been approved by the Secretary of State for Transport.  The decision of the independent reviewer is binding on both ACL and the carrier.

The available grounds for appeal are listed in Regulation 17(4) of the Airports Slot Allocation Regulations 2006 (see here for a link to the Regulation).  Failure to set out in full, in your request for a review, the specific grounds under Regulation 17(4) that you rely upon can invalidate your appeal.

The Misuse of Slots Enforcement Code (which is available here) sets out the procedure which you must follow in order to request an independent review, how the review will be conducted, your rights and the powers of the independent reviewer.

Importantly, the Code details what information and evidence you must include in your request and the deadlines that apply (a request for review must be lodged within fourteen days of the date of the Notice of Final Decision).

As any appeal to our decision to impose a penalty does not freeze the effect of the decision, the sanction itself remains active (i.e. a fine will remain payable).

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