Formed on 1 Nov 1916, 78 Squadron began its rotary wing career on 7 Jun 1965 at Khormaksar in Aden with nine Wessex HC.2 (delivered by RFA Sir Lancelot). It operated in support of British and South Arabian troops in Aden, developing new capabilities including the fitting of bomb racks and grew to operate 14 Wessex (including a SAR flight) by Jul 1967. As the situation deteriorated in Aden, it eventually withdrew in two waves to Sharjah in the UAE; the first 8 Wessex via HMS Fearless between 17 and 23 Oct 1967 and the second by 6 Wessex, on HMS Intrepid on 29 Nov 1967. On arrival, the SAR Flight detached and moved to RAF Muharraq (eventually to become COMSAR Bahrein) and 78 Squadron continued to operate in hot and sandy conditions. These eventually led to the units Wessex being temporarily repatriated singly to the UK by RAF Belfast freighters from Nov 1968 for a full strip down, clean out and re-assembly. Wessex strength had fallen to six airframes by Mar 1971 and the unit disbanded at RAF Sharjah on 21 Dec 1971 as part of Britains withdrawal from the Gulf.
When 78 Squadron reformed as part of the Falkland Islands Garrison, it amalgamated the Chinook HC.1s from 1310 Flight and the Sea King HAR.3s from 1564 Flight into the new unit.
It reformed at RAF Stanley in the Falkland Islands on 2 May 1986. 78 Squadron operated Chinook HC.2 and Sea King HAR.3As. Until 2004, the Sea Kings wore an overall grey for Combat SAR and utility missions, since then they reverted to the more usual high visibility yellow paint scheme.
From Nov 2007, the Squadron was reformed at RAF Benson as part of the Merlin force to fly the Merlin HC3a.
78 Squadron was reformed at RAF Benson on 3 Dec 2007, from a flight of 28 Squadron (then on detatchment in Iraq) and with the Merlin HC3, which will be supplemented with ex RDAF Merlins from 2008, into a Merlin pool; airframes are to be shared with 28 Squadron. 78 Sq was disbanded on 30 Sep 2014, and its Merlins were handed over to a newly reformed 846 NAS.