The A330 and A340 offered extensive commonality of cockpit systems, not only between themselves, but with the A320 – and, later, with other members of the A320 Family still to come. This made possible the Airbus concepts of cross crew qualification – pilots trained to fly one Airbus aircraft can qualify to operate another with relatively little extra training - and mixed fleet flying, in which airlines are able to switch their Airbus aircraft and their pilot crews at short notice to better match capacity to demand.