What does Block 19 on a flight strip represent for departing aircraft?

Block 19 on a flight strip for departing aircraft is utilized to convey essential details regarding the fix and the proposed departure time. This information is critical for air traffic controllers as it helps them coordinate the departure of the aircraft from the airport effectively. By having the proposed departure time, controllers can manage their traffic flow precisely and ensure that the aircraft is sequenced properly with respect to other departures and arrivals. Additionally, the fix indicates the initial point in the flight where the aircraft will start its intended route, which is vital for both situational awareness and ensuring compliance with air traffic procedures.

The other choices pertain to different aspects of flight operations. Altitude information typically appears in other designated blocks on the flight strip that directly relate to the aircraft's assigned or intended altitude. Actual time over fix is more relevant to in-flight tracking and is recorded separately once the aircraft has passed that designated location. The route of flight, while important, has its representation elsewhere on the flight strip, usually in a different block dedicated to detailing the entire intended route post-departure.