In 2013 the firm released the RM39-01 featuring a bold oversized round-shaped case made in grade 5 titanium which is commonly used in aircrafts and jets featuring a dual time flyback chronograph complication with day and month indication. Aviation has always been an important element to Richard Mille and the RM39-01 was the firm’s creation to satisfy their expectations to create a chronograph as complex as possible that would meet the requirements of the most experienced pilots as a professional flight navigation instrument. However the most defining feature on the watch is the E6-B slide rule which was first invented in the 1930s by Lieutenant Philip Dalton of the United States requiring no power supply making it an extremely safe tool for pilots. Featuring a fixed bezel and a bi-directional rotating bezel marked with complex indications it allows the wearer to track and calculate fuel consumption ground speed flight time density altitude and wind influence all converted to their respective unit of measurement. Secured with an innovative locking crown the component implemented prevents accidental activation of the chronograph eliminating risks of miscalculation.