Horizon-class frigate

The Horizon class is a class of air-defence destroyers in service with the French Navy and the Italian Navy, designated as destroyers using NATO classification. The programme started as the Common New Generation Frigate (CNGF), a multi-national collaboration to produce a new generation of air-defence frigates. In Italy the class is known as the Orizzonte class, which translates to "horizon" in French and English. The UK then joined France and Italy in the Horizon-class frigate programme; however, differing national requirements, workshare arguments and delays led to the UK withdrawing on 26 April 1999 and starting its own national project, the Type 45 destroyer.
The FREMM multipurpose frigate were built using the same company structure as the Horizon project.
Development.
France, Italy and the UK issued a joint requirement in 1992 after the failure of the NATO Frigate Replacement for the 90s (NFR-90) project. In July 1993, the three countries signed a Memorandum of Understanding for a Common New Generation Frigate (CNGF). The ships were to be armed with the Principal Anti Air Missile System (PAAMS). The UK intended to purchase twelve ships to replace its Type 42 destroyers. France was to purchase four to replace its and Italy would purchase six to replace its Doria class and Audace class.
Problems emerged almost immediately: the primary problem was that of differing requirements: France wanted anti-aircraft warfare (AAW) escorts for its aircraft carriers, but only a limited range was necessary due to the self-defence capability of . Italy too required only close-range capabilities, as in its home waters of the Mediterranean Sea the ships would operate under Italian Air Force cover or escorts for its aircraft carrier . The Royal Navy, however, required more capable ships which could throw a large defensive "bubble" over a fleet operating in hostile areas. The compromise which largely solved this problem was the adoption of a standard radar interface which allowed France and Italy to install the EMPAR multi-function passive electronically scanned array radar and the UK to install the more capable SAMPSON active electronically scanned array radar – the SAMPSON radar has a higher data rate and an adaptive beam that allows a greater ability to track multiple targets, long-range detection of low-RCS targets, a lower false-alarm rate, and overall higher tracking accuracy.
An agreement signed in March 1996 saw agreement that the PAAMS office would be based in Paris and the Project Horizon project office would be based in London. The latter was to be responsible for the design of the ship, its command and control and secondary weapons systems. Britain also agreed to contribute £100m in recognition of the development work already completed by Italy and France on PAAMS. Construction would be carried out by DCN (France), GEC-Marconi (UK) and Orizzonte (Italy). 
UK withdrawal.
On 26 April 1999 the UK announced that it was withdrawing from the CNGF project to pursue its own national design. At this point the CNGF project was five years behind schedule. The "Financial Times" summarised the main disagreements between the partner countries: 
The resulting Type 45 destroyer is armed with the PAAMS missile system and has benefited from investment in the Horizon project.
Franco-Italian project.
France and Italy continued their collaboration under the Horizon project. In September 2000, the two countries signed a contract to jointly produce four ships, ordering two ships each which would deploy the PAAMS missile system. The Italian Navy ordered two units, and , to replace the s. "Andrea Doria" was accepted on 22 December 2007 and received the flag of the Italian Navy. Full operation capability was achieved in the summer of 2008. The French Navy ordered two units, and to replace the carrier escorts. The project cost France €2.16bn (~US$3bn) at 2009 prices. A further two Horizons were cancelled; instead the two s were to be replaced by the FREDA air-defence variant of the Franco-Italian FREMM multipurpose frigate. France has bought forty Aster 15s and eighty Aster 30s for her ships.
On the Italian units the three cannon will be upgraded to the 76/62mm Super Rapid Multi Feeding David/Strales version with the capacity to use the DART guided projectile in the anti-missile role.