A locking device between a first structure and a second structure includes a bolt to lock the first and second structures, an indicator as to whether the bolt has locked/unlocked the structures, and a connecting system. The bolt includes a lock bolt attached to the first structure and able to engage a hook which is attached to the second structure. In particular, the connecting system connects the bolt with the lock bolt to the indicator, and the hook is mounted such that it can move between a first position in which it is engaged with the lock bolt and allows the indicator to be locked, and a second position in which the hook is free of the lock bolt and allows the indicator to be unlocked.