| May ask an aircraft to temporarily change its call sign for safety reasons when there is a risk of confusion between two or more similar call signs. |
| Must not ask an aircraft to change its call sign. |
| May require to change the call sign for safety reasons when there is a risk of confusion between two or more similar call signs providing the aircraft is on a repetitive flight plan. |
| May not ask an aircraft to change its call sign after accepting the flight plan. |
EN 