Macchi M.24

The Macchi M.24 was a flying boat designed by Alessandro Tonini and produced by Macchi in Italy during the 1920s. Originally intended as a bomber, it was eventually produced for civilian use as well. 
Design and development.
The M.24 resembled a scaled-up version of earlier Macchi flying boat bombers such as the M.9 and M.18, sharing their biplane configuration and Warren truss-style interplane struts. However, while these earlier aircraft were single-engine types, the M.24 had twin engines mounted in a tractor-pusher pair on struts in the interplane gap. Also like the M.18, it featured an open position in the bow for a gunner, but added a second such position amidships as well.
Two M.24s made a demonstration flight in 1925 from Macchi's home on Lake Varese, crossing the Alps to Amsterdam, Copenhagen, Stockholm, Leningrad and home again. This feat was followed by torpedo-launching experiments. The M.24 saw extensive use with the Italian Navy, and several were purchased by the Spanish Navy.
A civil version with equal-span wings was developed in 1927 as the M.24"bis". This featured an enclosed cabin within the forward hull that could seat eight passengers. "Aero Espresso Italiana" flew these on its Brindisi-Athens-Constantinople route, and SITAR operated them on routes in the Mediterranean as well.