Full circle: the story of air fighting. J. E. Johnson. 2001.

Air fighting began in the First World War, when single, fabric-covered aeroplanes scouted for the soldiers below. Pilots and observers fought aerial duels with rifles or revolvers. Soon the two-seaters were carrying machine-guns, and the scouts were flying in pairs. Later, the pairs developed into squadrons, and team fighting fighting developed until German ‘circuses’ of fifty vividly-painted scouts fought British ‘wings’. In the Second World War the Battle of Britain pilots fought in much the same way, but faster planes and greater altitudes brought a trend towards smaller formations. The introduction of jets saw  the fighting unit reduced still further and now, with supersonic fly-by-wire technology pushing the frontiers of air power ever further, formations have returned to single numbers. Air warfare has come full circle.