The term irony is here used in the sense pioneered in 1983 by Lisanne Bainbridge, to describe a solution which increases rather than reduces a problem. Bainbridge used the term in relation to automation, but it can be applied to other issues, particularly in how human factors engineering relies on training, procedures, design and automation as its main app­roaches to managing human variability. ‘Human factors’ tends to consider human agility or performance variability as a liability that should either be eliminated or brought under control. The paper encourages us to recognise that variability is an indispensable asset, without which few of the common human factors solutions would ever work.