UPDATE: New Requirements for UK-Area Airport Slots Effective Soon

PT 5 M minute read
UPDATE: New Requirements for UK-Area Airport Slots Effective Soon

This is a post by author Jason Hayward. Jason is general manager for Universal Aviation U.K. – London-Stansted. Jason is an expert on business aircraft operations in the U.K. and can be contacted at jasonhayward@univ-wea.com.

Amended airport slot procedures for the UK were implemented during the London Games in 2012. It’s been determined that these airport slot procedures will now be a permanent requirement for all arriving/departing flights at airports using the Airport Coordination Limited (ACL) slot system.

The following is an overview of what you need to know:

1. A short history on UK airport slot requirements

Recent changes to UK airport slot requirements are the result of a UK Civil Aviation Authority review at the National Air Traffic Management Advisory Committee. Notice of these changes, which take effect March 30, 2014, is under authorization of Article 14 of the European Commission Regulation 793/2004. It’s been decided to continue the use of "flight plan to airport" slot matching on an ongoing basis for most general aviation flights. Air ambulance, humanitarian, and emergency flights are exempted from these requirements. A new Aeronautical Information Publication (AIP) supplement, to be published March 20, 2014, will outline all applicable changes.

2. ACL slot-coordinated airports

ACL is a privately held company that coordinates airport slots for many airports around the world. ACL coordinates slots in the UK for Heathrow (EGLL), Gatwick (EGKK), Manchester (EGCC), Luton (EGGW), London City (EGLC), and Stansted (EGSS). Keep in mind that EGLL and EGKK typically have very few airport slots available, and operating to either of these two locations may require revising your schedule in order to accommodate restricted day-of-operation slot availability.

3. Obtaining airport slots

Unless an operator has its own airport slot account with ACL, standard practice is to request UK slots via a ground handler or Fixed-Base Operator (FBO). First, you’ll send your schedule to the ground handler or FBO. Next, they’ll log on to the Online Coordination System (OCS), search for the particular airport, and place your slot request times in the system. OCS will then inform what slots are available, and the ground handler or FBO (or an operator with an account) will choose the best available slot. Slot confirmations include a unique slot ID number. As of March 30, 2014, the slot ID number must be placed in remarks section 18 of the flight plan. Slot IDs are a 14-digit designator. The airport slot must have the prefix "ASL" attached to it when it is inserted into the remarks section 18 of the flight plan. An example of a remarks section 18 entry is:


The following is a breakdown of what is to be placed in the remarks section:

EGXX = (4 digits) airport ICAO designation
D = (1 digit) A = arrival or D = departure
SIG = (3 digits) made from suffix as held in the ACL system
000900 = (6 digits) made from flight number as held in the ACL system

If ASL is not placed in remarks 18 along with the slot ID, the system will detect the error and issue a warning – addressed to the originator of the flight plan. The flight plan originator will then need to correct the error. If corrective action is not then taken, it may result in the flight plan being removed from the Central Flow Management Unit (CFMU) system. Such an outcome might incur delays and the need to re-file a correct flight plan. Be mindful that the information held in the ACL OCS system must be accurate to afford the best possibility of a match between the flight plan and airport slot held.

4. Tips on using the slot coordination system

ACL is responsible for the slot request website and its operation, and this online resource is user-friendly. Individual operators have the option of requesting UK airport slots on their own by creating an account with ACL. There are fees to pay to create a slot request account. If setting up your own account, be aware that you’ll need someone with access to the system to make updates as needed in order to avoid day-of-operation issues if there are changes. For this reason, most operators choose to have ground handlers or FBOs take care of UK slot coordination.

5. Dealing with UK slots

UK slot confirmations are given on/off blocks and are not airborne/landing times. While ACL wants operators to adhere to approved slot times, a certain tolerance for each slot is provided. Deviation for an arrival slot is -20/+30 minutes, while deviation for a departure slot is -10/+30 minutes. Note that slot revisions are required for changes to schedule. However, revisions are not needed in the case of air traffic control delays or for mechanical issues that are resolved in less than two hours.

6. Filing your flight plan after obtaining a slot

It’s important to obtain an airport slot, when one is required, prior to filing a flight plan. Filing a flight plan before you have an approved slot will result in a warning to correct the filing. If no correction is made, your flight plan may be canceled or suspended. Fines may be imposed after this point, and it is ACL’s decision to enforce a fine or not.

7. Warning and fine considerations

Any changes to remarks section 18 of the flight plan must have the entire remarks section reentered. If you do not cancel a flight plan that’s no longer required, you will receive a warning, as this will be considered holding an airport slot you never intended to use. The same applies to flight plans that require alteration. Fines may be imposed for such errors, if you’ve received a warning and no corrections are made, that can reach up to 20,000 £ under the UK sanction scheme.

8. Always include a contact phone number in the flight plan

It’s imperative that a contact phone number be placed in remarks section 18 of your flight plan. This is required so that ACL is able to resolve discrepancies in a timely manner. The contact number is typically for the originator of the flight plan. But, it’s important that the originator make sure that someone is available, at the listed contact number, should ACL try to call.

9. Obtaining additional information

Information regarding new airport slot procedures that go into effect March 30 will not be available online until the AIP supplement is published March 20. It’s important that all operators comply with new UK airport slot requirements beginning March 30, 2014. ACL is working with operators to ensure all operators are aware of the new process.


It’s best to have your ground handler or FBO assist with slot coordination and flight plan filing for the UK to ensure that any changes/revisions to airport slots can be accomplished on time. It’s also important to ensure that all flight plans to UK slot-controlled airports are filed with remarks section 18 information completed correctly. Without the use of RMK/ASL, the flight plan matching system will be unable to make a successful match and will flag the discrepancy for correction.


If you have questions about this article or would like assistance planning your next trip to the UK, contact me at jasonhayward@universalaviation.aero.

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