ATPL: Morning Civil twilight begins when:
Domanda 121, General Navigation - ATPL - Airline Transport Pilot license
| The centre of the Sun is 6° below the celestial horizon |
| The Sun's upper edge is tangential to the celestial horizon |
| The centre of the Sun is 18° below the celestial horizon |
| The centre of the Sun is 12° below the celestial horizon |
