The invention provides a release for locking system particularly suitable for fastening a first element such as a panel (12) to a beam (35) adjacent to a second element, such as a another panel (42). The system is particularly useful for fastening panels on aircraft. The system includes a projection (32) for the first element (12), the projection having a locking cavity (44). Beam (35) includes an aperture (62) for receiving the projection (32). A locking means is adapted to engage the locking cavity (44) of the projection (32) when the projection (32) is received in the aperture (62), in order to lock the first element (12) to the beam (35), so as to be adjacent to the second element (42). The locking means includes material adapted to contract when activated, such as shape memory alloy wire (51, 52). The locking means includes engagement means (46) adapted to disengage the locking cavity (44) when the material (51 or 52) contracts. The invention also provides a second type of releasable fastening system. This has a shuttle (110) moveable between a locked position and an unlocked position. The system includes locking means (112, 108) for locking the shuttle (110) in the locked position and the unlocked position. This system also includes means such as shape memory alloy wire (121) for drawing the shuttle (110) to the unlocked position. The shuttle (110) is biased towards the locked position.