How accurate is flight time in a flight simulator?

In a general home flight simulator, airborne flight time can match a real flight within a few minutes when aircraft variant, route, weight, winds and speed profile match and the simulator runs at 1×. Gate-to-gate time is less predictable because real taxiing, ATC vectors, holding and schedule padding vary.

Here, flight simulator means a general consumer simulator unless we name a particular platform. Microsoft Flight Simulator 2020 and 2024, X-Plane 12 and DCS can all represent flight in real time, but their clocks, logbooks and time-acceleration controls do not necessarily measure the same thing.

Is a flight simulator real time?

Yes—at the normal 1× simulation rate, one simulated second is intended to equal one real second.

Three separate ideas are often confused:

• Real-world date and time: The simulator can set its clock and lighting to the real date and time, or to a custom value.
• Real-time simulation rate: At 1×, simulated time should pass at the same rate as wall-clock time.
• Realistic flight duration: The aircraft will reach its destination at a realistic time only if its route, groundspeed, weather and performance are also realistic.

Microsoft Flight Simulator is therefore real time when it is unpaused and running at 1×. Selecting live time does not lock the simulation rate, and selecting live weather does not guarantee that a recreated flight will match a historical journey.

To check a flight simulator timer, leave the aircraft parked and unpaused at 1×, record the simulator clock and an independent clock, then compare the elapsed intervals after several minutes. Their displayed time zones need not match; the elapsed minutes should. If they do not, check for a changed sim rate, a pause mode or performance severe enough to slow the simulation. MSFS users who are uncertain about the selected rate can follow our method for returning Microsoft Flight Simulator to normal 1× speed.

Which flight time should you compare?

Airborne time from lift-off to touchdown is the cleanest measure of route, wind and aircraft-performance accuracy. Different clocks start and stop at different stages, so two apparently conflicting durations may both be correct.

A mistake we see constantly is comparing an airline’s advertised gate-to-gate schedule with a simulator timer started on the runway. The simulated flight can appear 20 minutes shorter even though its airborne time and speed are accurate.

Does flight time include taxiing?

Sometimes: block time and many pilot-logbook definitions include taxiing, while airborne time does not.

• Airline schedules: Published flight times normally represent scheduled gate-to-gate or block time, including an allowance for departure and arrival taxiing.
• Actual airline operation: OUT-to-IN block time includes the ground interval between leaving the departure stand and reaching the arrival stand. OFF-to-ON airborne time excludes it.
• Pilot flight time: Under many fixed-wing logging definitions, time begins when the aircraft first moves for the purpose of flight and ends at the final stop after landing. Exact regulatory and operator rules vary.
• Simulator flight plans: ETE usually excludes destination taxiing and may begin at the runway, present position or first route waypoint.

If a comparison does not state whether taxiing is included, look for OOOI timestamps: OUT, OFF, ON and IN. These reveal whether the quoted duration is block time or airborne time.

What does a flight simulator timer record?

There is no universal flight simulator timer, so identify the clock before trusting its result.

A cockpit chronometer measures whatever interval the pilot manually starts. An FMS timer may show ETE to the next waypoint or destination. A Hobbs-style meter can follow engine or electrical operation, while an in-simulator logbook may use its own rules for detecting departure and arrival. Pause, Active Pause, replay and repositioning can affect these timers differently.

Why does simulator flight time differ from a real flight?

Most differences come from mismatched routing, wind, speed or timing definitions rather than an inaccurate simulator clock.

• Route distance: The same airports do not guarantee the same mileage. Runway choice, SIDs, STARs, airway restrictions, shortcuts and radar vectors can add or remove many nautical miles.
• Winds aloft: Duration follows groundspeed, not indicated airspeed or Mach alone. A strong headwind can extend the flight even when the correct cruise Mach is maintained.
• Aircraft variant: Engine type, aerodynamic model, payload and fuel load affect climb rate, optimum altitude and cruise performance. A correct livery does not mean the underlying aircraft variant is correct.
• Operating technique: Cost index, climb schedule, cruise Mach, step climbs, descent profile and speed restrictions all change elapsed time.
• Weather source: Live weather only matches a real flight taking place under the same conditions. Recreating an older flight with present-day winds is not a fair test. Our guide to setting up real-time simulator weather explains the distinction between live and manually selected conditions.
• ATC and traffic: Real flights receive vectors, holds, runway changes and shortcuts that may not exist in the simulated flight.
• Ground operations: Pushback, de-icing, runway queues and long taxi routes affect block time without changing airborne time.
• Simulation controls: Pause, slew, repositioning and altered simulation rates invalidate a wall-clock comparison. Under heavy processing load, some simulators may also fail to maintain the requested relationship between simulated and real time.

Even two real services using the same flight number can produce different airborne times on consecutive days. One simulator flight compared with one unrelated real-world result is weak evidence unless the route, runway, aircraft and weather also match.

How do you compare simulator and real flight time fairly?

A fair timing test recreates one real flight’s conditions and compares equivalent timestamps.

1. Choose the measurement. Use OFF and ON times when testing in-flight accuracy. Use OUT and IN only when reproducing the complete gate-to-gate operation.
2. Use UTC. Published departure and arrival times may use different local time zones or cross midnight. Convert both ends to UTC before calculating the duration.
3. Match the aircraft. Select the correct variant and engines where possible, then reproduce realistic payload and fuel. These factors matter most during climb and at high operating weights.
4. Recreate the route. Match the actual or filed runways, SID, airway route, STAR and approach rather than flying directly between the airports.
5. Match the performance plan. Use the intended cruise level, climb and descent speeds, cruise Mach or cost index, and any step climbs the aircraft supports.
6. Match the atmosphere. Reproduce the winds and temperatures for the real flight’s date and altitude. Surface weather alone is insufficient; cruise-level wind often has the largest timing effect.
7. Run at 1× without intervention. Do not pause, slew, teleport or accelerate time during a strict comparison.
8. Record checkpoints. Note UTC at take-off, top of climb, top of descent and touchdown. This shows where the difference developed instead of leaving one unexplained total.

A discrepancy present by top of climb points towards weight, temperature, climb schedule or aircraft performance. Time gained or lost steadily in cruise usually indicates wind, route distance, altitude or cruise speed. A difference appearing after top of descent commonly comes from the STAR, vectors, approach path and speed restrictions.

There is no universal acceptable error. Record both minutes and percentage: five minutes is substantial on a 30-minute sector but minor on a ten-hour flight.

How are ETE, Mach and airborne times calculated?

ETE is an estimate based mainly on distance remaining and groundspeed; Mach by itself does not determine arrival time.

For a constant-speed segment, the basic calculation is ETE (hours) = distance remaining (NM) ÷ groundspeed (kt). A 600 NM segment at an average groundspeed of 400 knots therefore takes 1.5 hours. A complete flight also includes changing speeds during climb and descent, turns, restrictions and possible route revisions.

Mach describes true airspeed relative to the local speed of sound. Temperature affects the true airspeed represented by a given Mach number, while wind converts true airspeed into groundspeed. Two aircraft flying at the same Mach can consequently have very different ETE values when one has a headwind and the other a tailwind.

An FMS normally refines ETE using route distance, forecast or sensed wind and the programmed performance profile. Simpler GPS units and HUD displays may extrapolate from present groundspeed, causing the estimate to change sharply during climb, turns or wind transitions. For the related calculation from ETE to clock time, see our explanation of how groundspeed and route distance determine estimated arrival time.

How do MSFS, X-Plane 12 and DCS time acceleration affect the result?

Time acceleration shortens the wall-clock wait but invalidates a real-time comparison.

At 4×, two simulated hours take roughly 30 minutes of wall-clock time if the simulator maintains that rate. The underlying flight still lasts about two simulated hours, so use the simulator clock rather than a stopwatch when measuring an accelerated flight.

For a strict accuracy test, return to 1× and confirm it before departure. If the aim is simply to shorten a long cruise, our guide to using time acceleration in MSFS, X-Plane and other simulators covers the available methods and their limitations.

Does matching flight time prove the simulator is realistic?

No—a matching duration does not prove that the aircraft’s aerodynamics, fuel burn or operating systems are accurate.

An aircraft can climb too slowly, cruise too quickly and still arrive at the correct time because the errors cancel out. A realistic flight simulator should match the timing of individual phases, the distance flown, groundspeed and fuel used—not merely the final elapsed time.

When a simulated flight appears much shorter than the airline schedule, compare OFF-to-ON airborne times before changing the aircraft’s speed. In most cases, the missing minutes are taxiing, schedule padding, a shorter route or different winds rather than a fast simulator clock.