[1] The engine was built in Spain as the Hispano-Suiza 5Q or Hispano-Wright 5Q without modification apart from the use of Hispano's patented nitriding finishing process.

[3] Wright finally ceased production of five-cylinder Whirlwinds in 1937,[3] concentrating on larger engines and leaving the market for small radials to companies like Kinner and Warner.

However, there were a couple of noteworthy exceptions which took advantage of the Whirlwind family's reputation for high reliability.

In 1935, the brothers Al and Fred Key set a new flight endurance record of 653 hours, 34 minutes in the Curtiss Robin J-1 Ole Miss, flying over Meridian, Mississippi, from June 4 to July 1.

Douglas "Wrong-Way" Corrigan's famous unauthorized transatlantic flight from New York City to Dublin, Ireland on July 17–18, 1938, used a Curtiss Robin with an R-540 built from the parts of two used engines.