Rohrbach Ro XI Rostra
The Rohrbach Ro XI Rostra was a flying boat built in Germany in 1928 for use as a transatlantic mail plane.It shared the same general configuration its predecessor, the Ro V Rocco: a conventional, high-wing flying boat with cruciform empennage and two engines mounted tractor-fashion in nacelles mounted on struts above the wing. The flight deck and cabin were fully enclosed. However, while the Rocco's wings had been braced by struts, the Rostra's wings were a fully cantilever design.
By late 1928, Philadelphia journalist Mildred Johnson was organising an east-to-west transatlantic flight aboard the Rostra, initially with three other passengers, but later as the sole passenger. In mid 1929, the Rostra made a preliminary 1,760 km (1,090 mi) round trip between Travemünde and Stockholm carrying ten passengers, and a longer-range flight to Iceland was planned.
3 + 5 seat flying boat intended to be used as a mail carrier cross the ocean
2 Gnôme-Rhône Jupiter VI
Length 15.60 m, height 6.30 m, span 26.90 m, wingarea 77.00 m2 aspect ratio 9,40
Empty 4340 kg, load 4060 kg, payload 1250 kg, flying weight 8400 kg  fuel 2450 kg oil 120 kg
Max. speed 213 km/h at sea level , cruising speed 158 km/h at sea level, climb 4,10 m/sec.  landing speed 118 km/h, range 2370 km, service ceiling 3000
m  endurance 15,00 m
First flight 30th of October 1928. Parts from the Robbe II were used. Tested but the engines were not powerfull
enough for the intended role as a trans atlantic mailcarrier