Why the need for the Flight Corridor Safety Program?

Removal of the trees will ensure Sea-Tac Airport complies with all Federal Aviation Administration (FAA) regulations protecting the takeoff and landing corridors off the airport runways. These trees, which pose a risk to aircraft safety, are either penetrating the airport’s airspace or soon will grow tall enough to penetrate the airport’s airspace.

  • FAA regulations require airports to identify and manage obstructions to navigable airspace on and around the airport
  • Removal of obstructions helps ensure safe operation of aircraft takeoffs and landings
  • Airports around the country manage similar programs to protect the safety of the flying public
FAA and State Regulations
Federal Aviation Regulation Part 139: Certification of Airports:

§ 139.331 Obstructions: In a manner authorized by the Administrator, each certificate holder must ensure that each object in each area within its authority that has been determined by the FAA to be an obstruction is removed, marked, or lighted, unless determined to be unnecessary by an FAA aeronautical study. FAA Advisory Circulars contain methods and procedures for the lighting of obstructions that are acceptable to the Administrator.

Federal Aviation Administration Advisory Circular 150/5300.13A, Airport Design:

Maintenance of obstacle clearance surfaces: Federally obligated airports are subject to Grant Assurances 20 and 21 which require the protection of the approach and departure surfaces. Airports operating under Code of Federal Regulations (CFR) Part 139 are also subject to Part 139.331 to mitigate obstructions. The airport operator has an ongoing obligation to review the surface(s) for obstructions. The FAA reviews all Instrument Approach Procedures (IAP) on a periodic basis; approximately every two years. Obstacles found within the associated approach/departure surfaces at that time may result in higher minima, loss of approaches and/or loss of night operations. (Note: This section was added in February, 2014.)

Grant Assurance 20:

The sponsor hereby assures and certifies, with respect to this grant that:
Hazard Removal and Mitigation. 20: It will take appropriate action to assure that such terminal airspace as is required to protect instrument and visual operations to the airport (including established minimum flight altitudes) will be adequately cleared and protected by removing, lowering, relocating, marking, or lighting or otherwise mitigating existing airport hazards and by preventing the establishment or creation of future airport hazards.

Federal Aviation Administration Engineering Brief #91: Management of Vegetation in the Airport Environment

To maintain land use compatibility around airports and protect surfaces associated with instrument and visual operations of the airport, it is recommended to protect terminal airspace by clearing bushes and trees that penetrate or have the potential to penetrate any applicable navigable surfaces. It is recommended that airport operators ensure protection of these operations by removing, lowering, relocating, marking, lighting, or otherwise mitigating existing objects and preventing the existence of objects surrounding the airport that could impair future operations.

Revised Code of Washington 14.12.020 Airport hazards contrary to public interest:

It is hereby found that an airport hazard endangers the lives and property of users of the airport and of occupants of land in its vicinity, and also, if of the obstruction type, in effect reduces the size of the area available for the landing, taking-off and maneuvering of aircraft thus tending to destroy or impair the utility of the airport and the public investment therein. Accordingly, it is hereby declared: (1) That the creation or establishment of an airport hazard is a public nuisance and an injury to the community served by the airport in question; (2) that it is therefore necessary in the interest of the public health, public safety, and general welfare that the creation or establishment of airport hazards be prevented; and (3) that this should be accomplished, to the extent legally possible, by exercise of the police power, without compensation. It is further declared that both the prevention of the creation or establishment of airport hazards and the elimination, removal, alteration, mitigation, or marking and lighting of existing airport hazards are public purposes for which political subdivisions may raise and expend public funds and acquire land or property interests therein.

Revised Code of Washington 14.12.010 Definitions:

(2) “Airport hazard” means any structure or tree or use of land which obstructs the airspace required for the flight of aircraft in landing or taking-off at an airport or is otherwise hazardous to such landing or taking-off of aircraft.

Examples of FAA Protected Surfaces          

7:1 Transitional Surface Example

(not to scale)

50:1 Approach Surface Example

(not to scale)

Obstruction Locations within FAA Protected Surfaces


The following maps identify the locations of obstructions that have been identified for removal.

FAA Surfaces and Obstructions Map

North Obstructions

South Obstructions

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