New ICAO Obstacle Limitation Surfaces (OLS)

Understanding the new ICAO OLS framework and what it means for UK aerodromes

In August 2025, ICAO adopted Amendment 18 to Annex 14, introducing a new, modernised Obstacle Limitation Surfaces (OLS) framework, representing the most significant change to aerodrome safeguarding in decades. The new OLS becomes applicable globally from 21 November 2030.

These changes affect all UK aerodromes, safeguarding authorities, developers, and organisations involved in airspace protection, obstacle assessment and planning.

The new framework replaces the long‑standing traditional OLS with a performance‑based, operations‑driven model, reflecting advances in aircraft performance, navigation, and procedure design.

Overview of the New OLS Framework

The previous ICAO OLS (in use since the 1950s) has been restructured into two major categories:

1. Obstacle Free Surfaces (OFS)

These surfaces ensure a kept‑clear volume of airspace where no obstacles are permitted, except existing terrain or previously assessed objects.

They are closely linked to:

• runway type
• aircraft Aeroplane Design Group (ADG)
• standard operations such as approaches, go-arounds, balked landings and take-off climbs

These surfaces represent the mandatory protected airspace needed for safe aircraft operations.

Key features include:

• Stricter obstacle control close to the runway
• Harmonised approach, transitional, and take-off climb surfaces
• Applicable to all runway types, not only precision runways in the old system

2. Obstacle Evaluation Surfaces (OES)

Instead of prohibiting obstacles outright, OES surfaces operate as triggering surfaces:

• If an obstacle penetrates an OES, it triggers an aeronautical study rather than automatic rejection.
• This reflects modern risk‑based and performance‑based evaluation principles.

OES account for:

• published instrument flight procedures
• aircraft performance
• operational intent
• ADG classification
• visual circuit patterns at aerodromes without procedures

This represents a major shift: penetration is manageable, not automatically unsafe, provided mitigations are established.

Aeroplane Design Group (ADG) – A Key Change

The new OLS is tied to the ICAO Aeroplane Design Group (ADG) classification, reflecting:

• aircraft wingspan
• indicated speed at threshold  (Vat)

Each ADG has corresponding OFS and OES dimensions.

This approach is more tailored to actual aircraft performance, improving safeguarding accuracy and avoiding unnecessary protected volumes at aerodromes that do not handle larger aircraft.

What the New OLS Means for UK Aerodromes

Aerodromes will need to:

• Update safeguarding maps and digital airspace models
• Understand differences in protected volumes (some areas expand, others reduce)
• Assess impacts on development proposals and planning safeguarding processes
• Coordinate with local planning authorities
• Review existing obstacles and update obstacle databases
• Implement new ADG‑based surface modelling
• Plan for transition ahead of 2030 applicability

The new OLS may reduce safeguarding burdens in some cases (less protected airspace), while expanding them in others.

Events, Workshops and Webinars

Upcoming New ICAO OLS Workshops

To support industry readiness ahead of the 21 November 2030 applicability date for the new ICAO Obstacle Limitation Surfaces (OLS), the CAA will be delivering a series of workshops throughout the year. These sessions are designed for aerodrome operators, safeguarding teams, planners, ANSPs, developers, and other stakeholders involved in obstacle management.

Confirmed Workshops

• 3 June 2026 – Manchester
• 17 July 2026 – Gatwick
• 8 October 2026 – Glasgow

Registration for this workshop is currently register‑interest only. Confirmation of available places will be emailed shortly to those who register.

🔗 Register here

What to expect from the workshops

Participants can expect sessions covering:

• Understanding and applying Obstacle Free Surfaces (OFS) and Obstacle Evaluation Surfaces (OES)
• Transition planning and implementation timelines
• Practical safeguarding case studies
• Interpreting ADG‑based surface changes
• Impacts on planning, development, and aeronautical studies

New OLS Webinar (Recording to be uploaded)

We are preparing a full webinar that introduces the new ICAO OLS framework, outlines the key changes, and explains what aerodromes and stakeholders need to do during the transition period.

Once complete, the webinar recording will be uploaded here, alongside:

• Presentation slides
• Q&A summary
• Supporting documents and guidance

This will allow stakeholders to access the material on demand and share within their organisations.

Stay Informed

We encourage stakeholders to revisit this page for updates as we release:

• Additional webinars
• Workshop materials
• Implementation guidance
• Transition resources

Why did ICAO update the OLS?

How do the new OLS interact with PANS OPS surfaces?

How will existing obstacles be treated under the new OLS?

Will aerodromes need to resurvey their obstacle environment?

How will the changes impact safeguarding maps submitted to planning authorities?

How do Aeronautical Studies under the new ICAO OLS compare to the safeguarding assessments we do today?