A method of controlling the motion of a turning aircraft during taxiing on the ground, the aircraft having a steerable landing gear, for example a nose landing gear, operating in a free-to-caster mode, includes (a) ascertaining the rotational position (Θ) of the steerable landing gear relative to the longitudinal axis (L) of the aircraft (b) receiving a control instruction that would, if effected, continue turning of the aircraft in the same direction away from the longitudinal axis, and (c) modifying the control instruction so that the angle between the rotational position of the steerable landing gear and the longitudinal axis will be lower than the angle that would otherwise be observed had the control instruction been effected and not so modified. The risk of damage to the steerable landing gear through over-steering may thus be reduced.