A drive system for an aircraft landing gear, the drive system comprising: a pinion gear; a drive shaft arranged to rotate the pinion gear about a drive axis; a driven gear arranged to mesh with the pinion gear to be rotatable by the pinion gear, the driven gear being connectable to a wheel of the landing gear to be capable of rotating the wheel about a wheel axis; and a flexible interface comprising a crowned spline joint between the drive shaft and the pinion gear. The crowned spline joint is arranged to permit tilting of the pinion gear relative to the drive axis. In some embodiments a first spline joint between the drive shaft and the pinion gear is arranged to permit tilting of the pinion gear relative to the drive axis; and a second spline joint is arranged to permit translation of the pinion gear along the drive axis relative to the drive shaft.