Obstacle height control
Learn about the approval you may need to obtain before carrying out any building development, using tall construction machinery, or berthing vessels, and how to apply for it.
Last updated 7 May 2026
Tall buildings, structures, equipment, vessels, and natural vegetation (‘tall obstacles’) can interfere with aircraft flight paths, radar systems, and navigation aids.
CAAS height clearance is required for tall obstacles that may affect aviation safety.
Who must apply for height clearance?
Anyone planning to erect, install, or operate structures or equipment that may affect aviation safety must apply for height clearance, including:
Qualified Persons (QPs)
developers and contractors
building and land owners, including government agencies such as NParks, PUB, and MINDEF
shipping agents arranging vessel berthing
What requires height clearance?
Any structure, equipment or activity that may affect aviation safety because of its height may require height clearance.
The examples below cover some common cases:
Permanent structures
buildings, including additions and alterations (A&A), solar PV panels, and other roof structures
towers, antennas, and masts
chimneys, lightning protection poles, and building maintenance units
Temporary structures
construction machinery such as cranes, rigs/piling machines and concrete pumps
rooftop or terrace features such as tents, sunshades, and awnings
Vessels
ships and other vessels during berthing
To confirm whether height clearance is required, please contact us.
When is height clearance required?
Whether height clearance is required depends on the obstacle’s height and its distance from the aerodrome.
Distance from aerodrome | Permanent structures | Temporary structures | Vessels (berthing) |
|---|---|---|---|
Less than 455m from runway centreline and areas under flight path within airport boundary | Clearance required for all structures regardless of height | Clearance required for all structures regardless of height | - |
More than 455m from runway centreline within airport boundary | Clearance required for structures taller than 5m | Clearance required for structures taller than 5m | - |
Beyond airport boundary | Clearance required if structure is above the threshold defined by CAAS | Clearance required if structure is above the threshold defined by CAAS | Clearance required if vessel is above the threshold defined by CAAS |
For construction machinery, use SkySAFE to check requirements. The interactive map will show whether your proposed activity requires clearance based on your location and height. For all other tall obstacles, please contact us.
Permanent structures
Permanent structures such as buildings require Permanent Structure Clearance.
Permanent Structure Clearance for a building is valid until the building is completed, i.e. at the Temporary Occupation Permit (TOP) stage.
Any Additions & Alterations (A&A) involving changes to the building height require a fresh height clearance application.
The actual as-built height must be declared upon completion, before TOP or Certificate of Statutory Completion (CSC) is obtained.
Temporary structures
Temporary structures, such as construction machinery and vessels, require Temporary Structure Clearance.
Temporary Structure Clearance is valid for the specific start and end dates approved in the application.
Each application may cover up to 15 construction machines at a single location.
Amendments may be made if there are changes to the height, duration, or type of machinery.
When and how to apply
Temporary Structure Clearance | Permanent Structure Clearance |
|---|---|
Submit your application on SkySAFE with complete information at least 7 working days (excludes Sat, Sun, and public holidays) before your proposed activity begins. | Submit your application to CAAS_ANSP@caas.gov.sg before applying for URA Written Permission. |
What information is required
Your clearance application must include the following:
date and duration of activity (for construction machinery)
address/location of the proposed structure or building
type of activity (building development, deployment of construction machinery, or vessel berthing)
proposed height of the structure or building
stringent control measures implemented on site to prevent height infringement
Contact information
Air Navigation Services Policy Division
CAAS_ANSP@caas.gov.sg