Aircraft that are capable of taking off and landing on bodies of water.


The development of water-based aircraft, or seaplanes, as they are called, was a natural outgrowth of the development of flight. In the early years of aviation, almost the only places where sufficiently long “runways” for takeoff and landing existed were along various bodies of water. Because almost one-half of the populations of the United States and Western Europe lived within close proximity to the coastline, the development of water-based flight became important.

Over the years, long over-water, or transoceanic, flights became a natural part of the transportation infrastructure. Yet, in many cases aircraft did not have the range to fly across the entire ocean nonstop. The development of seaplanes allowed for craft that could stop at islands or other harbors to refuel, do maintenance, or wait for improved weather before continuing on their way. Seaplanes also opened remote areas to travel, as they could land or take off on lakes, rivers, or harbors without requiring shore-based facilities.

The military, by the 1930’s, had taken a great interest in seaplanes. Naval vessels used catapult-mounted planes as forward scouts and observers. They could be landed on the sea and recovered back aboard ship for reuse. Seaplanes were also used for search and rescue by the military. They not only had long over-water flight capability, but also could set down on the water’s surface to pick up people. Some of these planes were also armed and used to hunt submarines, to lay mines, or to bomb torpedoes.

These uses, coupled with the dramatic increase in the number of flight passengers and the opening of regular transatlantic and transpacific mail routes in the years prior to World War II, led to the development of a number of different seaplane designs. Designers at Dornier, Sikorsky, Martin, Boeing, Grumman, and Consolidated all contributed to the variety of seaplanes available for both military and civilian use.


Seaplanes have been designed and built as two distinctly different types of aircraft. The first type, float planes, are essentially land-based aircraft modified for water takeoffs and landings. Float planes could be fitted with a single float under the fuselage and wingtip floats under the wings. Other aircraft manufacturers adapted their plane designs with twin floats under the hull. Manufacturers such as Cessna, DeHavilland, Grumman, and others have successfully adapted their aircraft to the rough conditions of water takeoffs and landings. These aircraft are prized for their ability to give access to remote areas. They are used for search and rescue and backcountry expeditions and as supply planes and tourist vehicles. Some are twin-engine planes, and others are single-engine planes. Due to the conditions of rough water, spray, and low visibility, however, all float planes have high-wing designs.

The second type of seaplanes, flying boats, have the rounded hull shape of a boat. The fuselage is designed so that it floats in, and not above, the water like float planes. This type of aircraft may also be equipped with wing floats. Flying boats are generally multiengined aircraft, with either two, three, or four engines. The number of engines depends upon the size of the plane and the range it is designed to fly over water. Flying boats also have a high-wing design, required not only by rough water, spray, and low visibility, but also by the fact that these planes land on their hulls in the water.

Commercial Aviation

The interwar years and, to some degree, the years during World War II, were a time of great success for commercial enterprises operating flying boats. One of the first companies to undertake long-haul, transoceanic service was Imperial Airways, formed in 1924 by the merger of four small companies, Handley Page Transport, Instone Air Line, Daimler Airway, and British Marine Air Navigation. Imperial’s goal was not only to unite the British Empire through air travel, but also to carry mail throughout the empire. Imperial Airways flew a number of different craft on its routes. In the early years, it flew small Supermarine Sea Eagle craft of the biplane style, with two wings placed one above the other and a single engine in between, with the propeller facing the rear. Sea Eagles were about 37 feet long, with a single Rolls-Royce 350-horsepower engine capable of flying at 93 miles per hour for all of its 200-mile cruising range.

Imperial Airways eventually expanded its service to include routes from England to Egypt, Australia, India, Kenya, South Africa, and Hong Kong. By the late 1930’s, Imperial was flying Short S-23 flying boats. These were known as C-class boats, and all had names beginning with the letter “C,” such as Cabot, Clio, Canopus, Coorong, and Cambria. C-class boats were very large vessels with a takeoff weight of nearly 40,000 pounds. They had four 910-horsepower engines, which gave them a top speed of almost 200 miles per hour over their 1,500-mile cruising range.

During this same period, another airline was establishing seaplane service in the United States also using flying boats. In 1927, Juan Terry Trippe merged a number of small airlines to create Pan American Airways, known as Pan Am. The airline flew primarily from the United States to points of call in Central and South America. When in 1928, the Foreign Air Mail Act, also known as the Kelly Act, began to allow U.S. commercial air carriers to be paid to carry United States mail overseas, Pan Am seized this opportunity to enlarge its fleet. The first vessels added were S-38 flying boats built by Sikorsky Aero Engineering Corporation.

As business expanded, Pan Am became America’s “official” airline. Although the U.S. government did not have financial investments in any airline, it was able and willing to help Pan Am compete against foreign state-run airlines such as Air France or Lufthansa. By 1931, Pan American had added the larger S-40 series to their fleet. These were the first of the Pan Am “Clippers” and carried thirty-two passengers.

By 1932, the S-42 series of vessels had begun to appear, and Pan American was looking to fly not only North, Central, and South American routes but also transatlantic and transpacific routes. S-42 aircraft were powered by four 700-horsepower Hornet radial engines and were capable of a 1,200-mile range. Although these craft turned out to be effective on the transatlantic run, they could not get all the way to Hawaii.

In 1935, the first of the real long-range flying boats were delivered to Pan Am for their Pacific service. The Martin 130 “China Clippers” were powered by four 950-horsepower Wasp engines, giving them a speed of 160 miles per hour and a cruising range of more than 4,000 miles. The first transpacific trip, from San Francisco, California, to Manila, the Philippines, took approximately 60 hours of flying.

By 1939, Pan Am had started to take delivery of the Boeing 314A, with a length of 106 feet, a wingspan of 152 feet, and a takeoff weight of 84,000 pounds. The four 1,600-horsepower Wright Cyclone engines could push the aircraft at 180 miles per hour for a cruising range of 3,700 miles. The first of these planes to fly was the “Dixie Clipper,” capable of carrying seventy-four passengers and a crew of ten. The Boeing 314A did not have wingtip floats for stability but instead had sponsons on the lower portion of the hull.

Military Aviation

Imperial Airways and Pan American Airlines were not the only beneficiaries of the new types of flying boats. The militaries of numerous countries were also involved in the design and manufacture of a variety of seaplanes.

German manufacturers designed and built a number of aircraft during this period. The Heinkel and Blohn und Voss companies both designed float planes and flying boats for the German military. Another successful designer and manufacturer of flying boats was Dornier. The Wal was a workhorse for Lufthansa in the 1920’s and 1930’s. In 1929, the Dornier DO-X made its maiden voyage from Lake Constance in Switzerland. It was the largest craft ever built at the time, with a wingspan of 157 feet, a length of 131 feet, and a weight of 48 tons. It was powered over a 1,000-mile range by twelve 600-horsepower engines.

During this time both Italy and France produced a number of flying boats. Both the Italian Macchi company and the French Latecoere company produced a number of designs. British companies such as Felixstowe, Sea Eagle, Iris, and Short all produced a number of designs for the Royal Navy during this period. Short, in particular, produced the Sunderland series, 85-foot-long craft with a 112-foot wingspan. The four 1,050-horsepower engines pushed the vessel’s 58,000-pound takeoff weight at 205 miles per hour over its 2,700-mile range.

In the United States, the Consolidated, Grumman, Sikorsky, Martin, and Boeing companies all contributed designs to the U.S. Navy’s flying boat fleet. Some of these designs, such as the Martin Mariner (PBM-3D), were used primarily as submarine hunters because of their 2,400-mile range.

During World War II, more than six thousand flying boats and float planes were produced by the United States, Russia, England, and Germany. This is a very large number of aircraft, but of the total, 3,290 of those were of one series, the Consolidated PBY series. The PBY-5 became known as the Catalina. The Catalina was 63 feet long with a wingspan of 104 feet. The twin 1,200-horsepower Pratt & Whitney engines drove the 34,000-pound aircraft at 190 miles per hour over its 4,000-mile range. These were some of the most versatile aircraft built for military service. They served as submarine hunters, coastal patrols, mine layers, search-and-rescue craft, and personnel carriers. They were built in a number of nations throughout the war.

The war years marked the end of an era for flying boats. The development of a large number of long-range aircraft and the building of the large number of airfields with runways capable of handling these planes made most flying boats obsolete. Some navies, including that of the United States, continued to develop flying boat prototypes for a number of years, but none of these were deployed to the fleet.

Contemporary Uses of Seaplanes

There remain places in the world so remote and with so little infrastructure that they are still serviced by seaplanes such as the Grumman Widgeon. The Widgeon is small, with a 31-foot length, a 185-mile-per-hour top speed, and a 1,00-mile range.

More recently, flying boats have made a comeback of sorts. They are not used for passengers or freight. Instead they are used, with special scoops attached, as firefighting aircraft. These vessels swoop down low over a lake or other body of water and scoop up a large volume of water and then return to the fire site to drop their water “bomb” on the fire.


  • Conrade, Barnaby, III. Pan Am: An Aviation Legend. Emeryville, Calif.: Woodford Press, 1999. An excellent history of the long-lasting airline, with much material on the use of seaplanes and some outstanding photographs.
  • Munson, Kenneth. Flying Boats and Seaplanes Since 1910. New York: Macmillan, 1971. A history of seaplanes that includes the major manufacturers in both the United States and Europe, with well-done color drawings and cutaways.
  • Oliver, David. Wings over Water: A Chronicle of Flying Boats and Amphibians of the Twentieth Century. Edison, N.J.: Chartwell, 1999. A well-written history of seaplanes, with color photographs.


Firefighting aircraft


Military flight

Rescue aircraft

Boeing’s 314A Clipper was one of the most famous seaplanes, carrying seventy-four passengers and a crew of ten.

(Library of Congress)