In the early 1970s, the RAF issued an Air Staff Requirement for the development of a new interceptor intended to replace both the Phantom and the Lightning.
An early proposal was McDonnell Douglas's plan for a Phantom with a variable-geometry wing.
This was rejected by the RAF owing to the fact that there was little apparent improvement in performance over the existing Phantom, and that it might affect the development of the "Multi-Role Combat Aircraft" (MRCA).
An alternative idea was to take the MRCA, which evolved into the Panavia Tornado, and develop an interceptor version.
The UK's partners in the MRCA project displayed no enthusiasm for the idea of developing an air defence version of the Tornado, so the UK alone began the process, and the authorisation for what came to be known as the Tornado Air Defence Variant (ADV) was issued in March 1976.
The initial plan was for the Tornado to replace the remaining two squadrons of Lightnings, as well as all seven squadrons of Phantoms.

While the Tornado was in development, the RAF looked at interim measures to replace the Phantom, which had been in service for over a decade by 1980, and was beginning to suffer from fatigue; one proposal considered was the possibility of leasing or purchasing F-15 Eagles to re-equip 19 and 92 Squadrons, the units stationed in Germany.
Further suggestions were that up to 80 F-15s be procured, to replace the Phantom and Lightning squadrons then in service, or even cancel the Tornado entirely and purchase the F-15 with UK adaptations (specifically to be fitted with the AI.24 Foxhunter radar developed for the Tornado, and capable of carrying the Skyflash air-to-air missile).

Ultimately, the F-15 option was not seriously considered, as it was felt there would not be time or cost savings over the Tornado ADV.
It was later decided that the Tornado, once it had entered service, would only re-equip three of the Phantom squadrons; two Phantom units would be retained in the UK, and two in Germany.
Ultimately, the Tornado replaced the Phantom in four squadrons - the two FG.1 units at RAF Leuchars (43 and 111 Squadrons), plus two FGR.2 units (23 and 29 Squadrons), while 56 and 74 Squadrons, and the two Germany based units (19 and 92 Squadrons) retained the Phantom.

In 1963, the prototype Hawker Siddeley P.1127 Short Take-Off and Vertical Landing (STOVL) aircraft undertook initial landings aboard Ark Royal, while three years later pre-production Hawker Siddeley Kestrel (which subsequently became the Harrier), conducted a series of extensive trials from HMS Bulwark, which proved the concept of using vertical landing aircraft aboard aircraft carriers.
At the same time, the 1966 Defence White Paper had laid out plans to withdraw all of the Royal Navy's conventional aircraft carriers, which would bring to an end the Fleet Air Arm's operation of fixed-wing aircraft from ships at sea, with it instead becoming a primarily rotary-winged organisation.
Because it was believed that 892 Naval Air Squadron would be the final carrier-based fixed-wing squadron to be commissioned into the Fleet Air Arm, their Phantoms each a capital Omega (Ω) letter on their tailfins, intended to symbolise their place at the end of the Royal Navy's era of fixed-wing aviation.

However, in the 1970s the Royal Navy was developing what was known as the "Through Deck Cruiser", a 20,000 ton ship with a full-length flight deck intended to embark a squadron of large anti-submarine warfare helicopters.
Almost as soon as the first ship, HMS Invincible, was ordered, another specification was added to the design: as well as the helicopters, a small squadron of STOVL aircraft would form part of the air group to act as a deterrent to long-range reconnaissance aircraft.
To this end, a navalised version of the Harrier was developed – over the life of the design process, the Sea Harrier's air defence role was augmented by responsibility for reconnaissance and maritime strike missions.
In March 1980, 14 months after 892 Naval Air Squadron was decommissioned and its Phantoms turned over to the RAF, 800 N
In the early 1970s, the RAF issued an Air Staff Requirement for the development of a new interceptor intended to replace both the Phantom and the Lightning. An early proposal was McDonnell Douglas's plan for a Phantom with a variable-geometry wing. This was rejected by the RAF owing to the fact that there was little apparent improvement in performance over the existing Phantom, and that it might affect the development of the "Multi-Role Combat Aircraft" (MRCA). An alternative idea was to take the MRCA, which evolved into the Panavia Tornado, and develop an interceptor version. The UK's partners in the MRCA project displayed no enthusiasm for the idea of developing an air defence version of the Tornado, so the UK alone began the process, and the authorisation for what came to be known as the Tornado Air Defence Variant (ADV) was issued in March 1976. The initial plan was for the Tornado to replace the remaining two squadrons of Lightnings, as well as all seven squadrons of Phantoms. 
While the Tornado was in development, the RAF looked at interim measures to replace the Phantom, which had been in service for over a decade by 1980, and was beginning to suffer from fatigue; one proposal considered was the possibility of leasing or purchasing F-15 Eagles to re-equip 19 and 92 Squadrons, the units stationed in Germany. Further suggestions were that up to 80 F-15s be procured, to replace the Phantom and Lightning squadrons then in service, or even cancel the Tornado entirely and purchase the F-15 with UK adaptations (specifically to be fitted with the AI.24 Foxhunter radar developed for the Tornado, and capable of carrying the Skyflash air-to-air missile). 
Ultimately, the F-15 option was not seriously considered, as it was felt there would not be time or cost savings over the Tornado ADV. It was later decided that the Tornado, once it had entered service, would only re-equip three of the Phantom squadrons; two Phantom units would be retained in the UK, and two in Germany. Ultimately, the Tornado replaced the Phantom in four squadrons - the two FG.1 units at RAF Leuchars (43 and 111 Squadrons), plus two FGR.2 units (23 and 29 Squadrons), while 56 and 74 Squadrons, and the two Germany based units (19 and 92 Squadrons) retained the Phantom.
In 1963, the prototype Hawker Siddeley P.1127 Short Take-Off and Vertical Landing (STOVL) aircraft undertook initial landings aboard Ark Royal, while three years later pre-production Hawker Siddeley Kestrel (which subsequently became the Harrier), conducted a series of extensive trials from HMS Bulwark, which proved the concept of using vertical landing aircraft aboard aircraft carriers. At the same time, the 1966 Defence White Paper had laid out plans to withdraw all of the Royal Navy's conventional aircraft carriers, which would bring to an end the Fleet Air Arm's operation of fixed-wing aircraft from ships at sea, with it instead becoming a primarily rotary-winged organisation. Because it was believed that 892 Naval Air Squadron would be the final carrier-based fixed-wing squadron to be commissioned into the Fleet Air Arm, their Phantoms each a capital Omega (Ω) letter on their tailfins, intended to symbolise their place at the end of the Royal Navy's era of fixed-wing aviation. 
However, in the 1970s the Royal Navy was developing what was known as the "Through Deck Cruiser", a 20,000 ton ship with a full-length flight deck intended to embark a squadron of large anti-submarine warfare helicopters. Almost as soon as the first ship, HMS Invincible, was ordered, another specification was added to the design: as well as the helicopters, a small squadron of STOVL aircraft would form part of the air group to act as a deterrent to long-range reconnaissance aircraft. To this end, a navalised version of the Harrier was developed – over the life of the design process, the Sea Harrier's air defence role was augmented by responsibility for reconnaissance and maritime strike missions. In March 1980, 14 months after 892 Naval Air Squadron was decommissioned and its Phantoms turned over to the RAF, 800 N
McDonnell Douglas Phantom in UK service