Water landing in the context of "Ethiopian Airlines Flight 961"

A seaplane is a powered fixed-wing aircraft capable of taking off and landing (alighting) on water. Seaplanes are usually divided into two categories based on their technological characteristics: floatplanes and flying boats; the latter are generally far larger and can carry far more. Seaplanes that can also take off and land on airfields are in a subclass called amphibious aircraft, or amphibians. Seaplanes were sometimes called hydroplanes, but currently this term applies instead to motor-powered watercraft that use the technique of hydrodynamic lift to skim the surface of water when running at speed.

The use of seaplanes gradually tapered off after World War II, partially because of the investments in airports during the war but mainly because landplanes were less constrained by weather conditions that could result in sea states being too high to operate seaplanes while landplanes could continue to operate. In the 21st century, seaplanes maintain a few niche uses, such as for aerial firefighting, air transport around archipelagos, and access to undeveloped or roadless areas, some of which have numerous lakes. In British English, seaplane is sometimes used specifically to refer to a floatplane, rather than a flying boat.

Air-sea rescue (ASR or A/SR, also known as sea-air rescue), and aeronautical and maritime search and rescue (AMSAR) by the ICAO and IMO, is the coordinated search and rescue (SAR) of the survivors of emergency water landings as well as people who have survived the loss of their seagoing vessel. ASR can involve a wide variety of resources including seaplanes, helicopters, submarines, rescue boats and ships. Specialized equipment and techniques have been developed. Both military and civilian units can perform air-sea rescue. Its principles are laid out in the International Aeronautical and Maritime Search and Rescue Manual. The International Convention on Maritime Search and Rescue is the legal framework that applies to international air-sea rescue.

Air-sea rescue operations carried out during times of conflict have been credited with saving valuable trained and experienced airmen. Moreover, the knowledge that such operations are being carried out greatly enhanced the morale of the combat aircrew faced not only with the expected hostile reaction of the enemy but with the possible danger of aircraft malfunction during long overwater flights. As such, many militaries have opted to develop a capable air-sea rescue component, and ensure that such assets are available during most deployments. Early air-sea rescue operations were performed by flying boats or floatplanes, with the first dedicated unit operating such aircraft being established near the final months of World War I. While initially restricted to in-shore operations and with limited equipment, capabilities and resources would be expanded over the following decades. By the start of World War II, various nations were operating capable air-sea rescue units that operated a combination of amphibious and land-based fixed wing aircraft.

An aircraft catapult is an acceleration device used to help fixed-wing aircraft reach liftoff speed (V_LOF) faster during takeoff, typically when trying to take off from a very short runway, as otherwise the aircraft engines alone cannot get the aircraft to sufficient airspeed quickly enough for the wings to generate the lift needed to sustain flight. Launching via catapults enables aircraft that typically are only capable of conventional takeoffs, especially heavier aircraft with significant payloads, to perform short takeoffs from the roll distances of light aircraft. Catapults are usually used on the deck of a ship — such as the flight deck of an aircraft carrier — as a form of assisted takeoff for navalised aircraft, but can also be installed on land-based runways, although this is rare.

Historically it was most common for seaplanes (which have pontoons instead of wheeled landing gears and thus cannot utilize runways) to be catapulted from ships onto nearby water for takeoff, allowing them to conduct aerial reconnaissance missions and be crane-hoisted back on board during retrieval, although by the late First World War their roles are largely supplanted by the more versatile biplanes that can take off and land on carrier decks unassisted. During the Second World War before the advent of escort carriers, monoplane fighter aircraft (notably the Hawker Hurricane) would sometimes be catapulted from "catapult-equipped merchant" (CAM) vessels for one-way sorties to repel enemy aircraft harassing shipping lanes, forcing the returning pilot to either divert to a land-based airstrip, jump out by parachute, or ditch in the water near the convoy and wait for rescue. By the time fleet carriers became the norm in WW2, catapult launches have become largely unnecessary and carrier-based fighter-bombers would routinely perform self-powered takeoffs and landings off and onto carrier decks, especially during the naval aviation-dominated Pacific War between the United States and the Empire of Japan. However, escalating arms races during the Cold War accelerated the adoption of the heavier jet aircraft for naval operations, thus motivating the development of new catapult systems, especially after the popularization of angled flight decks further limited the practical distance available as takeoff runways. Nowadays, jet aircraft can launch from aircraft carriers via either catapults or ski-jump deck, and perform optics-assisted landing onto the same ship with help from decelerative arresting gears.