Patrol aircraft

A maritime patrol aircraft (MPA), also known as a patrol aircraft, maritime reconnaissance aircraft, or by the older American term patrol bomber, is a fixed-wing aircraft designed to operate for long durations over water in maritime patrol roles — in particular anti-submarine warfare (ASW), anti-ship warfare (AShW), and search and rescue (SAR).

The first aircraft that would now be identified as maritime patrol aircraft were flown by the Royal Naval Air Service during World War I, primarily on anti-submarine patrols. At first, blimps and zeppelins were the only aircraft capable of staying aloft for the long periods of time (as much as 10 hours) needed by the patrols whilst carrying a useful payload. Shorter-range patrols were mounted by adapted landplanes such as the Sopwith 1½ Strutter. Later in the war, aircraft were developed specifically for the role. These were usually large floatplanes such as the Short 184 or flying boats such as the Felixstowe F.2. The U.S. Navy's Curtis NC long-range floatplanes were also designed and developed as ASW patrol aircraft, but they did not enter service until the war was over. In 1919, the Curtis NC-4 became the first aircraft of any kind to fly across the Atlantic Ocean, via New York City, Nova Scotia, Newfoundland, the Azores, and Lisbon, Portugal, and then continuing on to Southampton, England taking 19 days, proving the long-range capabilities of aircraft. Crossing the Atlantic in a zeppelin came later on.

...
Wikipedia