def METHOD_NAME(flight: Flight) -> str:
    takeoff_time = flight.flight_plan.takeoff_time()
    # Handle custom flight plans where we can't estimate the takeoff time.
    if takeoff_time is None:
        takeoff_time = timedelta()
    start_time = timedelta(seconds=int(takeoff_time.total_seconds()))
    return f"T+{start_time}"