Function fly_airship_inner 

fn fly_airship_inner(
    phase: AirshipFlightPhase,
    from: Vec3<f32>,
    to: Vec3<f32>,
    goal_dist: f32,
    leg_ctx_time_begin: f64,
    leg_duration: f32,
    context_tgt_end_time: f64,
    speed_factor: f32,
    height_offset: f32,
    with_terrain_following: bool,
    direction_override: Option<Dir>,
    flight_mode: FlightMode,
) -> impl Action<AirshipRouteContext>

The action that moves the airship.