This has been an unbelievable moment" - First load tests of the prototype Tension was running high in the Solar Impulse hangar at the start of the fuselage tests. Would the cockpit, the axles or the tail - the result of many years of research, calculations, simulations and tests - rupture? Would the fuselage bear the strain? The Solar Impulse team held their breath as 900 kg of lead were attached to the cockpit and 300 kg to each of the three axles. The load was gradually increased - first 20, then 50, 75 and finally 100.