After I claimed all World War 2 Caproni airplanes, it's about time to start delivering: First, Caproni's single-seat monoplane fighter line. The F.4 and the F.5 were developed at the same time, with the F.5 - using a readily available Fiat A.74 radial with (pathetic) 840hp - being ready first and indeed becoming the only Caproni monoplane fighter to be built in a two-digit number (12). She was slightly better than the MC.200 on paper, but came later and was considerably more expensive and complicated to produce, a disadvantage shared by all Caproni-Vizzola fighters. The F.4 with a 1.150hp DB601 engine was slower than the contemporary MC.202 and no better in all other respects, so only one was built. The F.6 was Caproni's equivalent to the Series 5 fighters (G.55, MC.205, Re.2005) and initially was designed around the domestically built Isotta-Fraschini Zeta 24-cylinder engine of 1.500hp. She was as good as the G.55 on paper, but shorter-ranged and more complicated and time-consuming to build; she was 100% Aluminium, of which the Italians had not much, and the unreliable Zeta engine needed 100-octane fuel, of which they had none (it made only 1.200hp on 87-octane fuel). The installation of a 1.475hp DB605 engine did not improve things; the initial version had a typhoon-style chin radiator which produced so much drag the plane was only good for 560kph, and the reworked prototype with a belly radiator which could go 630kph came too late and was discontinued in favour of the G.55, MC.205 and Re.2005.