Before commercial aviation emerged in the 20th century, property owners held unlimited rights to the air above their land. Traditional property laws held that whoever owned the soil owned anything below it and anything above it. However, the development of aviation led to the creation of a public easement for flights at altitude above private property.
Despite this public easement, a property owner still has the exclusive right to develop the vertical space above their property. (Zoning laws may limit this right by setting a maximum height for structures in a certain area.) A property owner may choose to sell their development right, which can result in substantial profits for property owners in urban areas. On the other hand, if a property owner does not use or sell their air rights, a neighbor cannot build a structure overhanging their property. These hangover structures are considered a trespass and can be removed by the owner of the ground below.
Navigable Airspace and Private Property Rights
Under the Federal Aviation Act, the federal government holds the authority to regulate the use of US airspace. The Federal Aviation Administration sets the rules for navigable airspace, in which all US citizens have a public right of transit. Navigable airspace includes space at or above the minimum altitude for flights, as well as the space needed for aircraft to safely take off and land. Most airspace now falls within this definition, since some new types of aircraft have no minimum flight altitude. The FAA also holds statutory authority to buy navigation easements around airports that allow planes to take off and land.
Property owners are entitled to compensation when the government or a trespasser substantially impairs the use of their property. This includes the airspace above their land. Formerly, courts considered whether a flight remained in navigable airspace as a threshold question in deciding whether substantial impairment had occurred. Modern decisions generally do not consider whether a flight remained within navigable airspace in deciding whether a substantial impairment occurred and whether a property owner is entitled to compensation.
Drones and Low-Altitude Flights
Unmanned aircraft known as drones are broadly available to the public and can fly at low altitudes over the property of others. Drone owners are free to fly these aircraft over private property, subject to FAA rules, without getting permission from the property owner. If a drone owner substantially impairs the property rights of a private party, though, they might face a civil lawsuit for compensation.
Freedoms of the Air for International Commercial Flights
Many commercial airlines fly their passengers around the world, which means that they must have permission to traverse the airspace of other countries. International aviation law addressed this issue in the Convention on International Civil Aviation (Chicago Convention) of 1944. Certain freedoms of the air arose from the Chicago Convention, as well as subsequent treaties and international practices:
The right to fly over a foreign country without landing
The right to land in a foreign country for fuel or maintenance, but without embarking or disembarking passengers or cargo
The right to fly from the home country to another country
The right to fly from another country to the home country
The right to fly between two foreign countries on a flight originating or ending in the home country
The right to fly between two foreign countries, or between two locations in a foreign country, with a stop in the home country for non-technical reasons
The right to fly between two foreign countries without flying across the home country
The right to fly within a foreign country after starting from or before continuing to the home country
The right to fly within a foreign country without starting from or continuing to the home country
The first five freedoms have been officially established by international treaties, such as the International Air Services Transit Agreement and the International Air Transport Agreement. In contrast, the last four freedoms are not officially established, but many countries have agreed to them. The Chicago Convention also laid the foundation for bilateral agreements and multilateral treaties that provide for international commercial air transport services. Air services agreements (or air transport agreements) cover matters such as the frequency and origins of flights, the airlines and types of aircraft that can fly between the countries, and tax issues.