The Sikorsky S-61N is one of the most versatile, dependable, and historically significant commercial helicopters ever built — a machine that helped define what rotary-wing aviation could achieve in the real world, far from the drawing board and the test range. The S-61N and its land-based sibling the S-61L were civil variants of the SH-3 Sea King military helicopter, developed during the late 1950s; where the S-61L dispensed with amphibious features for greater payload capacity, the S-61N retained the Sea King's floats, making it optimised for overwater operations. The S-61N made its first flight on 7 August 1962, and was subsequently updated to Mk II standard with more powerful General Electric CT58 engines offering better hot-and-high performance, along with vibration damping and other detail refinements. In Britain, the S-61N found two defining roles that between them wrote a remarkable chapter in aviation history. The first was the route from Penzance to the Isles of Scilly — a service started on 1 May 1964 when BEA Helicopters operated the first scheduled flight between Penzance and the Isles of Scilly with a Sikorsky S-61, a route that would continue under successive operators for forty-eight years. The second was the North Sea oil industry, where the S-61N became the backbone of offshore support operations. At the peak of North Sea operations in the 1970s, thirty S-61N daily flights were departing from Sumburgh Airport alone, supported by a round-the-clock maintenance operation, with individual aircraft averaging 100 hours per month and flying anywhere from the East Shetland Basin to the Danish coast. Bristow Helicopters also operated several S-61Ns on search and rescue operations from civilian bases at Stornoway, Sumburgh, Lee-on-Solent, and Portland between 1983 and 2007 — decades of quiet, vital, often dangerous work over some of the most unforgiving seas in the world. Between 1958 and 1980, Sikorsky built 794 S-61 series helicopters, of which 123 were S-61Ns — a relatively modest production run for a type whose impact on British aviation, island connectivity, and the energy industry has been quite disproportionate to its numbers. Rugged, reliable, and reassuring in the hands of those who flew it, the S-61N earned its place among the great workhorses of British skies.