Example systems and methods for controlling a flight of an aircraft subjected to a required time of arrival constraint at a target waypoint and to an additional flight criterion are disclosed herein. An example method includes calculating combinations of cruise speed and descent speed for estimated times of arrival (ETAs) at the target waypoint and determining a subset of the combinations that introduce substantially a same amount of time change in the ETA when changing the corresponding cruise speed to a cruise speed limit as when changing the corresponding descent speed to a descent speed limit. The example method also includes selecting a combination of the subset of the combinations having an ETA substantially equal to the RTA and modifying at least one of a cruise speed or a descent speed of the aircraft based on the selected combination.
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