How do I use time acceleration safely in FSX?

In Microsoft Flight Simulator X (FSX) and FSX: Steam Edition, press R, then + or - to raise or lower the simulation rate. Increase it one step at a time only in stable cruise, monitor the autopilot and scenery, and restore 1× before descents, turns, weather changes, busy airspace or landing.

How do I change the simulation rate in FSX?

Use the default R, then + or - sequence; these are consecutive keystrokes rather than a combination held together. FSX calls time acceleration the simulation rate.

1. Stabilise the aircraft: finish the climb or turn, trim the aeroplane and confirm that it is holding the intended course and altitude.
2. Select the simulation-rate command: press and release R.
3. Change one step: press + to accelerate or - to slow down. On many keyboards, the plus character shares the =/+ key and requires Shift.
4. Read the indication: FSX normally displays the selected rate briefly. Wait and observe the aircraft before increasing it again.
5. Return to normal: press R, then - as many times as necessary to reach 1×. Do not continue below 1×, because FSX also supports slow-motion rates.

If nothing happens, restore focus to the main simulator window and try the sequence again. Then open FSX's Controls settings and verify the commands for increasing and decreasing simulation rate; a customised keyboard profile may have replaced them. This is a control assignment, not an FSX.cfg performance setting.

These keystrokes apply to FSX and FSX: Steam Edition. Other simulators use different assignments, covered in our guide to simulation-rate controls in MSFS and other simulators.

What simulation rate is safe in FSX?

There is no universal safe maximum, because aircraft complexity, gauge coding, weather, traffic, scenery and frame rate all affect how well an accelerated flight behaves.

For an unfamiliar aircraft, treat 2× as the initial ceiling. Try 4× only when the aircraft has remained level and settled, no significant waypoint or altitude change is approaching, and FSX is loading scenery smoothly.

An add-on's published simulation-rate limit takes priority over this table. High frame rates do not guarantee that custom gauges, flight-management logic or failure systems support high acceleration.

Can I use FSX time acceleration with autopilot?

Yes, but accelerate only after the autopilot is genuinely tracking the route and holding altitude, not while it is capturing a heading, course or level-off.

A mistake we see often is selecting a high rate during a turn or immediately before a waypoint. The aircraft can overshoot, weave across the route or begin increasingly large pitch and bank corrections. Confirm the active heading, navigation, altitude and vertical modes first; our guide to setting and checking FSX autopilot modes explains those controls.

What should I do if the aircraft starts oscillating?

Reduce the simulation rate to 1× immediately rather than waiting for the autopilot to recover at the higher rate.

1. Restore normal time: use R and - until the display shows 1×.
2. Take control if necessary: disconnect the autopilot if the pitch or bank movements continue.
3. Stabilise and trim: return to the intended attitude, speed and altitude before re-engaging any mode.
4. Use a lower ceiling: remain at 1× or 2× for the rest of that flight.

Does FSX time acceleration affect fuel, airspeed and systems?

Time acceleration advances the simulator's clock and world; it does not command the aircraft to fly at a higher indicated airspeed. More distance is covered per real-world minute because the whole flight is progressing faster.

Fuel consumption still follows simulated time. If FSX sustains 4×, one simulated hour passes in roughly 15 minutes of real time, and the aircraft consumes approximately an hour's cruise fuel. Check quantity, tank selection and reserves before accelerating or leaving the flight unattended.

Engine operation, navigation, weather, AI traffic, failures and most system timers also advance. Custom add-on gauges may use timing methods that lose synchronisation at unsupported rates, so inspect engine indications, fuel balance, pressurisation and navigation modes after every increase.

Built-in ATC continues with the accelerated flight, leaving much less real time to hear and act on clearances. Return to normal before expected frequency changes, descent instructions, vectors or traffic conflicts.

Why does FSX stutter or show blurry scenery at high rates?

FSX stutters at high simulation rates because it has less real time to process each mile of aircraft movement, gauge logic, AI traffic, weather and incoming scenery.

• Return to 1× and allow terrain, textures and weather to catch up.
• Use a lower rate on the next attempt instead of repeatedly selecting the same unstable value.
• Reduce demanding AI traffic, scenery or weather settings if accelerated cruise is a priority.
• Use a simpler aircraft when custom systems are the limiting factor.

Selecting 8× does not guarantee eight times the real-world progress. If the simulator is pausing, loading constantly or updating the aircraft in large jumps, it has already exceeded its practical limit.

When should I return to normal speed?

Return to 1× well before any phase that requires a rapid control input, system change or ATC response.

• Before top of descent, altitude capture or a planned change in vertical speed
• Before route turns, waypoint sequencing, course interceptions or navigation-source changes
• Before entering turbulence, changing weather, high terrain or busy traffic
• Before ATC hand-offs, vectors and approach clearances
• Before an instrument approach, visual circuit, carrier operation or landing

After reducing the rate, recheck position, heading, altitude, speed, fuel, active navigation mode and approach preparation. Give the aircraft time to settle at 1× before starting the descent.

Is FSX time acceleration the same as Flight Simulator X Acceleration?

No. Flight Simulator X: Acceleration is the name of an expansion for the original boxed simulator, adding aircraft, missions and other features; simulation-rate control is built into FSX and does not require that expansion.

FSX: Steam Edition includes the Acceleration content. If you are deciding what the product name means rather than trying to speed up time, see our explanation of what the FSX Acceleration expansion contains.

Time acceleration is also different from Slew mode. Simulation rate keeps the flight and its systems running faster, while Slew repositions the aircraft outside normal flight physics; use our safe FSX Slew mode procedure if repositioning, rather than faster cruise, is your actual aim.