In 1931 Northrop built the prototype of an all-metal low-wing sporting monoplane, the Beta, a two-seater with a 119kW Menasco Buccaneer inline engine.
It was converted to single-seat high-speed mailplane configuration in 1933 and fitted with a 300 hp / 224kW Wright Whirlwind radial engine, in which form it became the first aircraft of such power to exceed 200mph / 322km/h.