An aircraft comprising an aircraft wing comprising a fixed wing and a wing tip device at the tip of the fixed wing, the wing tip device being rotatable relative to the fixed wing between: • a flight configuration for use during flight, and • a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that the span of the wing is reduced, the aircraft wing comprising a rotational joint comprising: a rotation mechanism that rotatably couples the wing tip device to the fixed wing, to allow the wing tip device to rotate relative to the fixed wing between the flight and ground configurations, and a locking mechanism comprising a locking bore (53, 54) and a locking pin that is receivable in the locking bore to lock the wing tip device in one of the flight or ground configurations, wherein the rotational joint further comprises an alignment mechanism comprising an alignment pin and an alignment bore (62, 63) and at least one of the alignment pin and alignment bore is tapered such that engagement of the alignment pin in the alignment bore acts to guide the locking bore and locking pin into alignment, characterised in that the aircraft comprises a control system configured such that the alignment pin is engaged in the alignment bore, to guide the locking bore and locking pin into alignment, before the locking pin is received in the locking bore to lock the wing tip device in the one of the flight or ground configurations. • a flight configuration for use during flight, and • a ground configuration for use during ground-based operations, in which ground configuration the wing tip device is rotated relative to the fixed wing such that the span of the wing is reduced, the aircraft wing comprising a rotational joint comprising: a rotation mechanism that rotatably couples the wing tip device to the fixed wing, to allow the wing tip device to rotate relative to the fixed wing between the flight and ground configurations, and a locking mechanism comprising a locking bore (53, 54) and a locking pin that is receivable in the locking bore to lock the wing tip device in one of the flight or ground configurations, wherein the rotational joint further comprises an alignment mechanism comprising an alignment pin and an alignment bore (62, 63) and at least one of the alignment pin and alignment bore is tapered such that engagement of the alignment pin in the alignment bore acts to guide the locking bore and locking pin into alignment, characterised in that the aircraft comprises a control system configured such that the alignment pin is engaged in the alignment bore, to guide the locking bore and locking pin into alignment, before the locking pin is received in the locking bore to lock the wing tip device in the one of the flight or ground configurations. a rotation mechanism that rotatably couples the wing tip device to the fixed wing, to allow the wing tip device to rotate relative to the fixed wing between the flight and ground configurations, and a locking mechanism comprising a locking bore (53, 54) and a locking pin that is receivable in the locking bore to lock the wing tip device in one of the flight or ground configurations, wherein the rotational joint further comprises an alignment mechanism comprising an alignment pin and an alignment bore (62, 63) and at least one of the alignment pin and alignment bore is tapered such that engagement of the alignment pin in the alignment bore acts to guide the locking bore and locking pin into alignment, characterised in that the aircraft comprises a control system configured such that the alignment pin is engaged in the alignment bore, to guide the locking bore and locking pin into alignment, before the locking pin is received in the locking bore to lock the wing tip device in the one of the flight or ground configurations.