the United Kingdom were leased to cover the gap. This lease ran out in 2003, without the Typhoon being ready for service. The solution was provided by a five-year lease of 34 F-16s, with an option to extend the lease for another five years. 30 aircraft were F-16A/B Block 15ADFs while the remaining four were earlier-block aircraft for spares. These were all used US Air Force fighters. In June 2010, the Italian Air Force started the return of the F-16s to the United States which was completed on 23 May 2012, when all the Italian F-16s were returned to the US. The Italian Foreign Military Sales program was known as PEACE CAESAR. Future operators Bulgaria It was reported in December 2012 that Bulgaria was going to negotiate buying eight or nine second-hand fighter jets. Among the contenders were the Swedish Gripen, second-hand Italian Eurofighters and second-hand Portuguese F-16s. Later, in January 2013, it was reported that the Bulgarian Defense Ministry was expected to buy nine F-16s from Portugal. The final phase of the initial preparations was to be started by the middle of 2013. However, widespread protests led to the resignation of the Borisov cabinet, which delayed all government plans and activities. A new round of negotiations for the purchase of second-hand Greek F-16s had started by the middle of 2014. Possible negotiations with the US were also expected, with hopes of reaching a decision over the procurement in 2015. In July 2015, the government of Bulgaria approved negotiations with Belgium, the Netherlands and Greece for the procurement of second-hand F-16s. The increasingly pressing issue of MiG-29 maintenance, which had been pushing on the deadlines of the procurement, was expected to be resolved by an agreement with Poland for the repairs of the jets' engines. The decision was further delayed beyond 2015 because no money had been set aside for the purchase. To alleviate the issue of air defence, the Ministry of Defence proposed to allow other NATO members to conduct air-policing missions with the Bulgarian Air Force. By then, only four Bulgarian MiG-29s had enough flying capacity left to conduct air policing. This nearly led to the stepping down of the Bulgarian Air Force Commander at the time, Rumen Radev, as a protest against the Defence Ministry's plan to conduct joint air-policing missions. He stated that the overhaul of MiG-29 engines was only a temporary solution, with the purchase