the intended recipient does not receive the clearance, and fails to take up the desired heading or routing, or fails to climb or descent to the cleared level;
the controller misunderstands the intentions of aircraft under his/her control;
the controller issues a clearance to the wrong aircraft, and/or fails to issue a clearance to the intended aircraft;
the workload of controllers and pilots is increased because of the necessity to resolve the confusion.
Recognising the risk associated with similar call signs, EUROCONTROL is investigating the possibility of implementing system solutions aimed at removing the risk potential as early as the flight planning phase and by involvement of Central Flow Management Unit (CFMU).
European Action Plan for Air Ground Communications Safety