What point should be used to compute estimated time en route on an IFR flight plan?

The point of first intended landing is the correct choice for computing the estimated time en route (ETE) on an IFR flight plan because it represents the destination point where the flight will ultimately conclude. This point is significant as it allows the pilot to calculate the time required to reach the designated landing area while incorporating the aircraft's average speed and any relevant adjustments for wind and weather conditions along the route.

Moreover, using the point of first intended landing aligns with standard flight planning practices and is essential for ensuring that the flight duration is planned accurately to coincide with air traffic control operations and airport arrival procedures. By focusing on this point, pilots can more effectively manage fuel requirements, approach procedures, and readiness for possible holding patterns or diversions if needed on final approach.

In contrast, other choices like the final approach fix or the initial approach fix are points associated with the approach and landing phases but do not represent the total journey to the destination. The closest waypoint, while perhaps useful for navigation, does not signify the planned endpoint of the flight and therefore is not suitable for estimating overall travel time.