Aviation 101: Protecting Navigable Airspace

By Arthur J. Park

The Federal Aviation Administration (FAA) has recognized that the airspace around an airport is subject to the utmost protection. The Federal Regulations concerning runway protection zones and obstructions to air navigation are rather complex, but the most basic provisions relating to obstructions to navigation are found in 14 C.F.R.1 Part 77 entitled Safe, Efficient Use, and Preservation of the Navigable Airspace. Additional requirements are found in Grant Assurances contained within federal funding as well as easements with neighboring landowners.

Federal Regulations

Part 77 establishes (a) the requirements to provide notice to the FAA of certain proposed construction; (b) the standards used to determine obstructions to air navigation; © the process for aeronautical studies of obstructions to air navigation to determine the effect on the safe and efficient use of navigable airspace; and (d) the process to petition the FAA for discretionary review.2

First, section 77.9 establishes a number of situations in which a party is required to give notice to the FAA of a proposed construction within three nautical miles of a public use airport.3 For the purposes of this article, there are three important calculations that trigger the notice requirements. To wit, any proposed construction that would exceed an imaginary surface extending outward and upward at any of the following slopes: (a) 100 to 1 within 20,000 feet; (b) 50 to 1 within 10,000 feet; or (c) 25 to 1 within 5,000 feet.4 These protected slopes essentially allow for safe departures and landings at the airport.

If you are required to file notice under section 77.9, you must submit to the FAA a completed FAA Form 7460–1, Notice of Proposed Construction or Alteration.5 The form must be submitted at least 45 days before the start of the proposed construction.6 These notice requirements give the FAA the opportunity to review and approve proposed construction around public airports and ensure that the navigable airspace is protected. The failure to file a Form 7460 with the FAA can lead to the creation of unsafe, dangerous hazards to air navigation that threaten and risk the lives of pilots landing and taking off from the airport.

Second, an obstruction to air navigation can include “any object of natural growth, terrain, or permanent or temporary construction.”7 “Objects that are considered obstructions under the standards described in this subpart are presumed hazards to air navigation unless further aeronautical study concludes that the object is not a hazard.”8 Under the federal obstruction standards, the following types of object are deemed an obstruction to air navigation:

  1. A height of 499 feet AGL9 at the site of the object.
  2. A height that is 200 feet AGL, or above the established airport elevation, whichever is higher, within 3 nautical miles of the established reference point of an airport, excluding heliports, with its longest runway more than 3,200 feet in actual length, and that height increases in the proportion of 100 feet for each additional nautical mile from the airport up to a maximum of 499 feet.
  3. A height within a terminal obstacle clearance area, including an initial approach segment, a departure area, and a circling approach area, which would result in the vertical distance between any point on the object and an established minimum instrument flight altitude within that area or segment to be less than the required obstacle clearance.
  4. A height within an en route obstacle clearance area, including turn and termination areas, of a Federal Airway or approved off-airway route, that would increase the minimum obstacle clearance altitude.
  5. The surface of a takeoff and landing area of an airport or any imaginary surface established under § 77.19, 77.21, or 77.23. However, no part of the takeoff or landing area itself will be considered an obstruction.10

Section 77.19 then describes the civil airport imaginary surfaces: (a) horizontal surface, (b) conical surface, © primary surface, (d) approach surface, and (e) transitional surface.11 For example, the approach surface extends for a horizontal distance of:

i. 5,000 feet at a slope of 20 to 1 for all utility and visual runways;

ii. 10,000 feet at a slope of 34 to 1 for all non- precision instrument runways other than utility; and

iii. 10,000 feet at a slope of 50 to 1 with an additional 40,000 feet at a slope of 40 to 1 for all precision instrument runways.12

Similarly, Georgia regulations provide that an obstruction is “[a]ny penetration of an airport imaginary surface described in Federal Aviation Regulation Part 77 and FAA Advisory Circular 150/5300-13.”13 In Georgia, an airport hazard is defined as “[a]ny structure, object of natural growth, or use of land which obstructs the defined runway primary surface, safety area, and approach/ departure paths surfaces applicable to that particular airport.”14 Georgia regulations also require the following unobstructed approach and departure paths: (a) 15:1 slope for runways less than 4000 feet; and (b) 20:1 slope for runways greater than 4000 feet.15 “All penetrations of the approach and departure paths, whether natural or manmade, constitute an obstruction to navigation and a violation to licensing standards.”16

Finally, under 14 C.F.R. sections 77.25 et seq., the FAA has discretion to undertake an aeronautical study and determine whether an obstruction to air navigation (as defined above) has such an effect on the safe and efficient use of navigable airspace to constitute a “hazard.”17 To successfully challenge a FAA hazard/ no hazard determination in court, the petitioner must demonstrate that the FAA’s action was arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law.18

Grant Assurances

\When airport owners or operators (sponsors) accept funds from FAA-administered airport financial assistance programs, they must agree to certain obligations (assurances). These contractual obligations require the recipients to maintain and operate their facilities safely and efficiently and in accordance with specified conditions. The assurances are often attached to the application or the grant for federal assistance and become part of the final grant offer.19 In exchange for federal funds, the sponsor agrees to assume certain responsibilities pertaining to the safe conduct of flight operations at the airport and for the benefit and safety of the flying public. The standard Grant Agreement includes the obligation to maintain the Runway Protection Zone free of obstructions to air navigation. These obligations and assurances currently included the following relevant terms:

19. Operation and Maintenance.

a. The airport and all facilities which are necessary to serve the aeronautical users of the airport, other than facilities owned or controlled by the United States, shall be operated at all times in a safe and serviceable condition and in accordance with the minimum standards as may be required or prescribed by applicable Federal, state and local agencies for maintenance and operation. It will not cause or permit any activity or action thereon which would interfere with its use of airport purposes…

In furtherance of this assurance, the sponsors will have in effect arrangements for –

  1. Operating the airport’s aeronautical facilities whenever required;
  2. Promptly marking and lighting hazards resulting from airport conditions, including temporary conditions; and
  3. Promptly notifying airmen of any condition affecting aeronautical use of the airport…

20. Hazard Removal and Mitigation.

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.

21. Compatible Land Use.

It will take appropriate action, to the extent reasonable, including the adoption of zoning laws, to restrict the use of land adjacent to or in the immediate vicinity of the airport to activities and purposes compatible with normal airport operations, including landing and takeoff of aircraft…20

In short, “[f]ederally obligated airports are subject to Grant Assurances 20 and 21 which require the protection of the approach and departure surfaces… The airport operator has an ongoing obligation to review the surface(s) for obstructions.”21 It is interesting to note that Grant Assurance 20 shifts the burden of “removing” hazards from the FAA to the airport sponsor; the FAA generally does not have authority to force a private landowner to remove, lower, or relocate an existing hazard to air navigation.

An obstruction survey at the airport should identify those objects that may affect aircraft operations.22 Furthermore, “any existing or proposed object, whether man-made or of natural growth that penetrates these surfaces [in Part 77] is classified as an ‘obstruction’ and is presumed to be a hazard to air navigation.”23 If an obstruction cannot be feasibly removed, the danger should be mitigated by lighting and marking it.24


Airport sponsors often obtain a clear zone easement (sometimes referred to as an aviation easement) with adjacent landowners to protect the approach and departure surfaces existing within the Runway Protection Zone of the airport from obstructions. Under such an easement, the airport sponsor is generally vested with actual and constructive control over the property for purposes of preventing and removing obstacles to air navigation.

“The RPZ’s function is to enhance the protection of people and property on the ground.”25 This is best achieved through airport owner control over RPZs, including the acquisition of sufficient property interest and clearing RPZ areas of incompatible objects and activities.26

As the United States Supreme Court has recognized, “the Federal Aviation Administration (FAA) has been given broad authority to regulate the use of the navigable airspace, in order to insure the safety of aircraft and the efficient utilization of such airspace and for the protection of persons and property on the ground.”27 The importance of protecting navigable airspace is highlighted in the federal regulations, grant assurances, and local easements. Airports, consultants, and adjacent landowners must continue to vigilantly safeguard the navigable airspace for departures and landings.

Arthur J. Park is a partner with Mozley, Finlayson & Loggins LLP in Atlanta, practicing in the areas of aviation litigation, subrogation, civil defense, and insurance coverage


1 Code of Federal Regulations.
2 14 C.F.R. § 77.1.
3 14 C.F.R. § 77.9.
4 14 C.F.R. § 77.9(b). The measurements are taken “from the nearest point of the nearest runway of each airport described in paragraph (d) of this section with its longest runway more than 3,200 ft. in actual length.”
5 14 C.F.R. § 77.7(a).
6 14 C.F.R. § 77.7(b). “(a) If you propose any construction or alteration described in § 77.9, you must provide adequate notice to the FAA of that construction or alteration.” 14 C.F.R. § 77.5(a).
7 14 C.F.R. § 77.13. 8 14 C.F.R. § 77.15(b).
9 Above ground level.
10 14 C.F.R. § 77.17(a).
11 14 C.F.R. § 77.19.
12 14 C.F.R. § 77.19(d)(2).
13 Ga. Comp. R. & Regs. 672-9-.01®.
14 Ga. Comp. R. & Regs. 672-9-.01(d).
15 Ga. Comp. R. & Regs. 672-9-.03(A).
16 Id.
17 See also 49 U.S.C. § 44718(b)(1).
18 Town of Barnstable, Mass. v. F.A.A., 740 F.3d 681, 687 (D.C. Cir. 2014).
19 Grant Assurances (Obligations) – Airports (last visited July 6, 2016).
20 www.faa.gov;(Grant Assurances dated March 2014) (website last visited July 6, 2016) at pp. 9-10 (emphasis added).
21 FAA Advisory Circular 150/5300-13A (Sept. 28, 2012) at p. 12.
22 Id. at p. 44.
23 Id. at p. 58.
24 Id. at p. 73. See also FAA Advisory Circular 70/7460-1K (Obstruction Marking and Lighting).
25 FAA Advisory Circular 150/5300-13A (Sept. 28, 2012) at p. 71.
26 Id. The Runway Protection Zone is further defined and calculated in FAA Advisory Circular 150/5300-13A (Sept. 28, 2012) at pages 71-75.
27 City of Burbank v. Lockheed Air Terminal Inc., 411 U.S. 624, 627 (1973) (quotations omitted).