US Patent 10144505 Aircraft flight control using a required time of arrival index

A method includes receiving, at a flight management system of an aircraft, a required time of arrival (RTA) of the aircraft at a first location. The method includes receiving, at the flight management system, an input indicating an RTA index value. The method further includes modifying a speed of the aircraft based on the RTA and the RTA index value. The speed is determined by the flight management system as part of a flight plan of the aircraft.