The story so far...
1936 - Italian Navy issues request for a Very Long Range MPA. Savoia Marchetti tries to update its S55, but eventualy cooperates with CANT in producin a twin hull flying boat, essencialy a couple of Z501 hulls with the larger wing (enlarged further) and three engines of the Z508. The machine takes off with all its engines, to be able to lift its huge fuel load, then cruises with two engines. The Aircraft is called the SMZ101.
1938 - Fear of carrier fighter interception leads to a request for a Very long Range seaplane fighter to protect the SMZ101. Macchi tries an experimental double hull evolution of its M41 biplane seaplane fighter, then develops a monoplane version. A very elegant machine, with two slim hulls and powered by two Fiat A74 engines. Armed with four 12.7mm, the MC99 machine proves surprisingly fast and manouvrable.
1940/43 - The SMZ101bis, in service in small numbers, proves so succeful as a ASW aircraft that larger number of a "ter" version are introduced. The MC99 is extremly succeful in action against RN Fulmars and a bis version with DB601 engines is tried. in 1942 the final 995 version with DB605 engines enters production. The most curious version was a double seater (a bubble cockpit in each hull) night fighter with german radar.
A few SMZ101ter operated over the Atlantic in support of the italian submarine operations. They were extremely succeful and were regarded by the RN as posing a therat as serious as the LW Condors. Dornier tested an experimental German bigger equivalent, based on a double hull Do26 with six engines, but it remained a prototype.