It has long been accepted within the aircraft industry and others, that the number of man-hours needed to produce successive units or batches of units decreases. This effect is called ‘learning’; and a plot of the man-hours required per unit set against the production number is called a ‘learning curve’. Similarly a plot of unit cost (at constant economic conditions) against production number is also called a learning curve, since cost is related to the number of man-hours required.

When the production costs of future aircraft are estimated, learning has to be simulated. This is generally done using curves chosen from a standard family of ‘learning curves’ generated by a simple parametric equation; a curve is chosen on the basis that it is the best-fit by the standard equation to the out-turn data from previous similar projects.