For an IFR flight plan, what point should be used to compute estimated time en route?

The correct choice for computing the estimated time en route for an IFR flight plan is the point of first intended landing. This is because the estimated time en route calculation is primarily based on the distance to the destination and the average groundspeed of the aircraft. By using the point of first intended landing, pilots take into account the entirety of the flight from departure to arrival, allowing for a more accurate assessment of time needed for the entire segment of the journey.

Additionally, considering the first waypoint after departure focuses on only the initial segment of the flight, which does not provide a comprehensive view of the entire route. Using the middle of the flight route could lead to incomplete calculations, as it may not accurately represent the distance remaining to the destination. The point where the aircraft climbs to cruise altitude also doesn't account for the entire flight duration since time spent climbing is only a small portion of the total flight time. Therefore, the point of first intended landing provides the most appropriate reference for calculating the estimated time en route on a professional and accurate basis.