United States v. Causby

The common-law maxim that ownership of land extends indefinitely upward has no place in modern aviation. Airspace generally functions as a public highway, and recognizing unlimited private ownership of all air above land would make ordinary air travel vulnerable to innumerable trespass actions.

But a landowner must control the immediate reaches of the airspace above the surface to make full use of the land. Buildings, trees, and fences necessarily occupy that space. Thus, the owner has a property interest in at least the airspace that the owner can occupy or use in connection with the land, even if the owner has not physically filled it with structures.

The relevant question is not whether an airplane physically touches the ground. It is whether the invasion is so direct and immediate that it subtracts from the owner's beneficial use and exploitation of the land. Repeated flights through the low airspace above the Causbys' farm had that effect, much as an elevated railway at the same height would have imposed a servitude even without supports on the land.

The flights were not merely consequential injuries from a generally lawful activity, such as the ordinary noise and smoke produced by a nearby railroad. The Government repeatedly used the airspace immediately over the Causbys' land, and that direct invasion destroyed the property's commercial use as a chicken farm and diminished its value.

The Court did not establish a precise altitude boundary for protected airspace. Instead, it held that flights are compensable only when they are sufficiently low and frequent to create a direct and immediate interference with the use and enjoyment of the land. The Court of Claims' factual findings plainly met that standard here.

Federal aviation statutes declared navigable airspace to be public and defined it as airspace above the minimum safe altitudes prescribed by the Civil Aeronautics Authority. The Government argued that its aircraft were exercising this public right of transit.

The Court distinguished a landing or takeoff glide path from the regulatory minimum safe altitude of flight. The applicable minimum safe-altitude regulations generally prescribed heights far above the approximately 83-foot flight path over the Causbys' property. A glide path describes how an aircraft operates while landing or taking off; it does not itself define the lower boundary of navigable airspace under the statute.

Treating every airspace corridor needed for landing and takeoff as public navigable airspace would permit flights so low that they made land uninhabitable without compensation. That result would contradict the Government's own concession that such extreme interference would be a Fifth Amendment taking.

The Court of Claims had statutory authority to hear claims founded on the Constitution, as well as certain contract claims against the United States. Because the low-level flights imposed a compensable easement under the Fifth Amendment, the Causbys' claim was constitutional in character.

The Court therefore had no need to decide whether repeated governmental trespasses could also create an implied contract. The established taking supplied an independent and sufficient basis for jurisdiction.

A taking transfers a defined property interest to the United States, so the easement must be described with sufficient precision. The findings did not specify such essential terms as the flights' permissible altitude, frequency, aircraft type, or duration.

Although the Court of Claims' opinion referred to a permanent easement, that statement could not substitute for formal findings of fact supported by evidence. Its conclusion that the Government probably intended a lasting arrangement appeared conjectural rather than evidentiary.

Whether the easement was temporary or permanent materially affected the amount of compensation. Because the record did not establish the nature of the interest taken, the Supreme Court could not review the adequacy of the $2,000 award and remanded for necessary findings.