A step climb in aviation is a series of altitude gains that improve fuel economy by moving into thinner air as an aircraft becomes lighter and becomes capable of flying in the thinner air at a higher altitude.
By climbing gradually throughout the cruise phase of a flight, pilots can make the most economical use of their fuel.
The step climb intervals may be 1,000 or 2,000 or 4,000 ft (300 or 610 or 1,220 m), depending on the flight level rules which apply on the particular airway being flown.
Concorde, for example, used a continuous cruise climb throughout its flights, since there was normally never any other traffic at the same altitude (nearly 18,000 m (60,000 ft)) in the same direction.
These "rules" do not consider the effects of different winds at different levels; computerised flight planning systems may be better at height optimisation, and may even include 'step descents' in certain weather conditions.