How do pilots file flight plans?

Pilots file flight plans through the appropriate air traffic services prior to departure to ensure safe and efficient management of air traffic. This process involves submitting the necessary information about the flight, such as the intended route, altitude, and estimated departure and arrival times, which is crucial for air traffic controllers to manage the flow of air traffic and maintain safety in the sky.

Filing through air traffic services provides a centralized and regulated approach to flight planning, allowing for immediate communication of flight alterations or emergencies, which is vital for safety and coordination among various aircraft in flight. This method also ensures that the flight adheres to applicable regulations and receives necessary clearances for takeoff and landing.

The other options do not reflect the established process for flight planning. Airline operations typically involve other aspects of flight management but are not the method through which individual flight plans are filed. Requests made solely to ground control at the airport would not encapsulate the required protocols for air traffic management. Additionally, submitting requests to an aircraft manufacturer does not align with the operational procedures of flight planning, as manufacturers do not handle live air traffic operations.