An aircraft (101) includes a ground manoeuvre control unit (226) for automatically controlling ground manoeuvres. The aircraft (101) has control mechanisms (230) such as a rudder, nose wheel steering, spoilers, wheel brakes (110a and 110b) and the like for controlling motion of the aircraft (101). The control unit (226) is configured to receive lateral input demands (220) concerning lateral motion of the aircraft (e.g. heading control) and longitudinal input demands (222) concerning longitudinal motion of the aircraft (e.g. deceleration). The control unit (226) passes on the input demands (220, 222) as output demands (228) to the relevant control mechanisms (230) of the aircraft (101) with, if so required, a modification which prioritises one of the lateral input demand (220) and longitudinal input demand (222) based on the risk of a lateral runway excursion and the risk of a longitudinal runway excursion (232).