See how FSX Flight Planner estimates fuel, flight time and headings, why its nav log can be inaccurate, and how to plan reliable figures.
FSX Flight Planner splits the chosen route into waypoint legs, totals their distances, estimates each leg’s time from the selected aircraft’s cruise performance, and derives fuel burn from that time and the aircraft’s native performance data. Its headings describe planned leg directions; they are not dependable wind-corrected headings to hold in the cockpit.
This applies to both Microsoft Flight Simulator X and FSX: Steam Edition. The planner is useful for approximate routing, but it is not an aircraft-performance or airline dispatch system.
What does FSX use for each nav-log figure?
The FSX navigation log combines route geometry with simplified assumptions about the selected aircraft.
| Figure | How FSX estimates it | Main limitation |
|---|---|---|
| Distance | Totals the geographical distance between each pair of route waypoints. | Excludes taxiing, ATC vectors, holding and procedures not included in the route. |
| Flight time | Applies an assumed aircraft cruise speed to each leg’s distance and adds the leg times. | It is not a detailed climb, cruise and descent calculation or a forecast of actual groundspeed. |
| Fuel | Uses the estimated time with simplified native aircraft and engine performance data. | It does not provide a complete fuel load covering taxi, reserve, diversion or holding fuel. |
| Heading | Derives the planned magnetic direction from one waypoint to the next. | It is a route course rather than a guaranteed nose heading corrected for wind. |
The route type has a large effect on these figures. A Direct-GPS plan may be close to the shortest geographical route, while VOR-to-VOR and airway plans add intermediate fixes and therefore distance. Our guide to FSX route types and the navigation log explains how those choices alter the generated plan.
The entered cruise altitude becomes part of the plan and may influence routing or the performance estimate, but it does not make FSX model a complete vertical profile. There are no detailed step climbs, company climb schedules or arrival fuel predictions.
Why can the estimated time and fuel be inaccurate?
FSX’s estimates become inaccurate when its generic assumptions differ from the way the aircraft is actually flown.
- Wind changes groundspeed: a headwind increases time and fuel burn, while a tailwind reduces both. Do not assume the planner has produced a leg-by-leg winds-aloft forecast.
- Climb and descent are simplified: a heavily loaded jet may spend considerable time climbing below cruise speed and at high fuel flow.
- Power and mixture settings matter: piston-aircraft fuel burn changes with power, altitude, propeller setting and mixture leaning.
- Custom aircraft may bypass native assumptions: an add-on using its own engine, fuel or flight-management logic may not match the data available to the FSX planner.
- Operational fuel is omitted: taxiing, an alternate airport, missed approaches, holding and reserves require additional fuel.
Microsoft does not expose the planner’s fuel calculation as an auditable dispatch worksheet. Treat the displayed fuel as predicted trip burn under simplified conditions, not as the exact quantity to place in the tanks. For a safer loading method, use our FSX trip-fuel and reserve calculation.
Are Flight Planner headings the same as cockpit headings?
No: the nav-log heading is effectively the planned direction of the route leg, while the aircraft’s nose may need to point elsewhere to counter wind.
If the planned course is 090 degrees and the wind pushes the aircraft south, holding 090 on the heading indicator will not maintain the intended track. You must apply a wind-correction angle, or use navigation equipment capable of tracking the required course. The distinction between the heading shown on the instrument and the path over the ground is covered in our explanation of heading, course, bearing and wind correction.
On a long Direct-GPS leg, the required course can also change gradually along the great-circle path. FSX GPS guidance updates the desired track during the leg, whereas a printed nav-log figure should not be treated as one heading to hold indefinitely.
FSX also uses its own navigation database and magnetic-variation model. Consequently, a planner heading or VOR course can differ from modern real-world charts; when flying within FSX, use the simulator’s matching navigation data rather than mixing data from different eras.
How should you use the FSX estimates?
Use the Flight Planner figures as a first-pass check, then replace its assumptions with performance data for the aircraft and conditions being flown.
- Select the aircraft first. The planner needs the intended aircraft’s performance data; planning with one aircraft and then changing to another makes the estimate irrelevant.
- Choose the correct route and cruise altitude. Generate the route, then inspect the navigation log for unnecessary detours or an unexpectedly short direct leg.
- Calculate a realistic groundspeed. Adjust cruise true airspeed for forecast wind rather than using airspeed as though it were groundspeed.
- Allow for every flight phase. Add taxi, climb, descent, approach and likely ATC delays instead of treating the displayed ETE as gate-to-gate time.
- Build a complete fuel load. Start with trip fuel, then add the reserves and contingency appropriate to the type of flight.
- Regenerate after changes. Recalculate the route after changing aircraft, route type, waypoints or cruise altitude so that the navigation log reflects the final plan.
For aircraft whose speed, range and flight-level data are known, an aircraft-specific spreadsheet planning tool offers more control than relying solely on FSX’s generic estimates. Complex add-ons may also include their own performance calculator or flight-management system, which should take precedence over the built-in planner.
What if the estimate is obviously wrong?
An implausible estimate usually indicates the wrong aircraft, an unexpected route or aircraft data that the built-in planner cannot interpret well.
- Confirm that the intended aircraft was loaded before the route was generated.
- Compare the total distance with a rough direct distance; airway routing can create a substantial detour.
- Check for repeated, missing or badly ordered waypoints in the navigation log.
- Regenerate the plan rather than trusting figures left over from an earlier aircraft or route.
- For a custom aircraft, compare the planner’s estimate with the aircraft documentation or a measured cruise fuel flow from a stable test flight.
The route and total distance are usually the most useful outputs. Flight time, fuel and headings should be treated as starting values that still require wind, aircraft-performance and operational corrections.