A seaplane becomes a subject of admiralty law only when it is on sea and is considered to be a marine object subject to the maritime law of salvage.  Thus, a seaplane stored for repair in a hangar on dry land is not a vessel and is not a subject of admiralty law.  Conversely, a hydroplane is considered to be a vessel and is subjected to admiralty jurisdiction insofar as it is used on the sea.  A hydroplane is not deemed to be a vessel while being used as an airplane because law does not consider means of transportation usable exclusively in the air as a vessel.

“A helicopter being used in place of a vessel to ferry personnel and supplies to and from an offshore drilling structure is considered to be engaged in maritime activity.”

Courts often look for a significant relationship to traditional maritime activity in order to ascribe maritime character or status.[i]  This is because admiralty jurisdiction required not only maritime situs, but also maritime status.[ii]  Thus, the crash of a land-based aircraft on a flight between points within the continental United States could not invoke admiralty jurisdiction merely because the plane crashed in navigable waters.

The term special maritime and territorial jurisdiction of the United States, includes “any aircraft belonging in whole or in part to the United States while such aircraft is in flight over the high seas, or over any other waters within the admiralty and maritime jurisdiction of the United States and out of the jurisdiction of any particular state, as well as certain space vehicles while in flight.”[iii]

[i] Exec. Jet Aviation v. City of Cleveland, 409 U.S. 249 (U.S. 1972)

[ii] Id.

[iii] 18 U.S.C.A. § 7(6)