of "Tranche 2" in December 2004, this tranche will see the RAF receive a further 89 aircraft, bringing its Typhoon inventory to 144. This followed protracted negotiations regarding the early introduction of ground attack capabilities of the aircraft and hence its swing-role capability. While this was always planned it was intended to come at a much later date. Typhoon FGR4 Single-seat Block 5 or later aircraft (built or upgraded from F2) are known as Typhoon FGR4s. The new mark number represents the increased capabilities of the Block 5 aircraft (fighter/ground attack/reconnaissance). The FGR4 has from June 2008 achieved the required standard for multi-role operations. Typhoon T3 Two-seat Block 5 or later aircraft (built or upgraded from T1) are known as Typhoon T3s. As of June 2018, the RAF has 67 Tranche 2 Typhoons and has contracted to purchase 40 Tranche3 Typhoons. 107 Tranche2 and3 Typhoons will be modified via "Project Centurion", allowing them to utilise Meteor missiles, Brimstone and Storm Shadow missiles. 24 Tranche1 Typhoons will be retained for UK Quick Reaction Alert purposes, and will not be modified under Centurion. No. IX Squadron, based at RAF Lossiemouth, retains the Tranche1 Typhoon for QRA purposes but also serves the purpose of acting as an aggressor aircraft, similar to that of the USAF Lockheed Martin F-16 Fighting Falcon. These aircraft work in conjunction with the 100 Squadron BAe Hawk T.1 aircraft based at RAF Leeming, providing air combat training and dogfight training to RAF and Royal Navy pilots. In December 2021, the Ministry of Defence stated RAF Typhoons had shot down a drone in Syria, making this their first operational air-to-air engagement. Proposed versions Navalised Typhoon Owing to the withdrawal of France from the Eurofighter 2000 project, in part due to France's desire to have a greater role in the development and marketing of the aircraft, the pursuit of a naval Typhoon has never seriously been considered. However, a navalised variant of the aircraft was first proposed in the late 1990s as a potential solution to the UK Royal Navy's need for a Future Carrier-Borne Aircraft (FCBA) for its new (Queen Elizabeth-class) aircraft carriers, In January 2001, the UK Ministry of Defence formally discounted the option of a navalised Eurofighter for its new aircraft carriers, in favour of the Joint Strike Fighter, which (at that time) promised to be a capable, low-cost and more stealthy aircraft that would enter into service