FAA Airspace, Airports and Height Limits for Data Centers

Most data centers are one to three stories, so airspace can seem irrelevant. It is not. Data centers are often sited on flat, open land near highways and industrial areas, which is exactly where general aviation and regional airports tend to be. The FAA’s notice criteria slope up gently from runway ends, so a modest building close to a runway can still need review.

The elements that stick up are often the issue: generator exhaust stacks, rooftop cooling equipment, lightning protection masts, communication antennas, substation structures and the transmission poles that bring power to the site. During construction, tower and mobile cranes reach far higher than the finished building.

Federal regulations at 14 CFR Part 77 require anyone proposing construction or alteration that meets certain criteria to notify the FAA. The main triggers are:

A 100:1 slope rises one foot for every 100 feet of distance. That means a structure 10,000 feet from a qualifying runway triggers notice at roughly 100 feet in height, and one 5,000 feet away at roughly 50 feet, adjusted for the difference between site and runway elevations. Roads, railroads and waterways next to a structure are counted at the height of the vehicles that use them, which can push a borderline project over. Additional criteria apply in some situations, such as when the FAA asks for notice of a specific proposal.

The FAA’s Obstruction Evaluation / Airport Airspace Analysis (OE/AAA) website provides a notice criteria tool that checks a set of coordinates and height against these rules. It is a fast first screen for any site within a few miles of an airport.

1. 01Prepare accurate coordinates and elevations for each structure, crane position or point that meets the criteria. Surveyed data matters because small errors in ground elevation change the result.
2. 02File FAA Form 7460-1, Notice of Proposed Construction or Alteration, through OE/AAA at least 45 days before construction begins or before the date an application for a construction permit is filed, whichever is earliest.
3. 03The FAA studies the proposal against obstruction standards, instrument procedures, radar and navigational aids, and may circulate it for public comment if there is a potential hazard.
4. 04The FAA issues a determination of no hazard, often with marking and lighting conditions, or a notice of presumed hazard that can lead to negotiation over height or location.
5. 05Once construction reaches its greatest height, file Form 7460-2 when the determination calls for it to report actual construction.

A determination of no hazard generally expires 18 months after its effective date unless construction has started, and extensions can be requested. On long-horizon campus phases, track expiration dates and refile as designs change.

Filing notice is not the same as being a hazard. Part 77 also defines obstruction standards and a set of imaginary surfaces around each runway: the primary, approach, transitional, horizontal and conical surfaces. A structure that penetrates these surfaces is an obstruction and gets closer review, but the FAA can still find it is not a hazard after evaluating its effect on flight procedures and operations.

The approach surfaces off runway ends are the most restrictive. A site directly in line with a runway faces lower effective height limits than a site the same distance to the side. Runway protection zones, which extend from runway ends, are areas airports try to keep clear of buildings and people altogether, and development there is usually discouraged or controlled by the airport.

• Wildlife attractants: FAA guidance discourages stormwater ponds, open water and other features that attract birds within set distances of airports. A large campus with wet detention ponds may need dry basins or other designs near an airfield.
• Exhaust and thermal plumes: high-velocity vertical plumes from generator stacks or large heat rejection equipment can create turbulence for low-flying aircraft and may be raised in airport review.
• Electromagnetic interference: large metal structures and some equipment can affect radar and navigational aids, which the FAA considers in its study.
• Glare: reflective roofs or solar arrays near approach paths may need glare analysis.
• Military airspace: proximity to military installations, training routes or radar can add review through the Department of Defense.

Wildlife and plume concerns tie directly to campus design. Stormwater strategy, generator placement and cooling equipment all interact with the airport, so it is worth raising them during layout rather than after engineering is complete.

The FAA does not issue building permits or enforce height limits on private land; its determinations are advisory. Local governments do. Many communities around airports have airport overlay zones or height hazard zoning that turns the FAA surfaces into enforceable limits, and some add land use compatibility rules for noise and safety zones. Some states require a separate state aviation permit for tall structures near airports. Requirements vary by state and jurisdiction.

That means airspace belongs in zoning for data centers and the data center permitting process, not just in a separate FAA track. When we screen sites near airports, we run the notice criteria for the tallest likely structures and crane positions and check the local overlay at the same time.