Command line options 2020.3

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Note  This article presents the command line options for FlightGear version 2020.3.x. To check the current command line options, including for the development version, see the Command line options article.

Legend how to read the following options

  1. --option1 (--option2) - in this case --option2 is the aliast for --option1 which is exactly the same as --option1.
  2. --option1
    --option2 - two different options, mutually exclusive. They cannot be used simultaneously, but are connected due to a common description.
  3. --option1, --option2 - two different options that can be used simultaneously and are connected due to a common description.

General Options

--help (-h)

Show the most relevant command line options.

--verbose (-v)

Show all command line options when combined with --help or -h.


Display the current FlightGear version.


Specify the root data path.


Specify the base scenery path. Defaults to $FG_ROOT/Scenery.


Specify additional aircraft directory path(s) (alternatively, you can use --aircraft-dir to target a specific aircraft in a given directory).


Specify a path to addon. Multiple instances can be used.


Store aircraft and scenery downloaded via the simulator in path. The TerraSync directory may be specifically set with the --terrasync-dir option.


Specify an additional base data directory (FGData), before the $FG_ROOT directory.


Enable/disable automatic scenery downloads/updates.


Specify the TerraSync scenery path. Defaults to $FG_HOME/TerraSync.


Select the language for this session. Available codes: ca, de, en, es, fr, it, nl, pl, pt, ru, tr, sk, zh.


Run Qt Launcher. Without this option, it will immediately start the simulator in the default configuration or in the configuration read from the fgfsrc file - if it exists.


Enable/disable splash screen.


Enable/disable extra mouse pointer (i.e. for full screen Voodoo based cards).


Specify path to your web browser.


Set the given property to the given value. Type can be one of string, double, float, long, int, or bool.


After starting the simulator, open the properties dialog immediately on the given property. If you need more windows, just add more browser indexes like browser[1], browser[2] etc., for example:
which will open two dialogs with the given properties.


Load additional properties from path.


Do not load any default configuration files (like fgfsrc) unless explicitly specified with --config.


Use feets (default) or meters for distances.


Allow Nasal scripts to read files from directories listed as path (separate multiple paths with a semicolon (Windows) or a colon (UNIX)). By default, for security reasons, Nasal scripts can only read data from certain directories, such as $FG_ROOT, $FG_HOME, etc.


Make $FG_HOME read-only.


Ignore the autosave file, i.e. the settings saved in this file will not be loaded during startup, nor will the settings be saved to this file when closing the simulator.


Allow/Disallow save preferences upon program exit.


Reset all user settings to their defaults (rendering options etc.)


Enable headless mode.


Log JSBSim properties. An output directives file contains an <output> element, within which should be specified the parameters or parameter groups that should be logged. See JSBSim Logging.



Enable/disable 2D instrument panel.


Start in a pause state or unpause.


Fuel tank quantity forced to remain constant or fuel is consumed normally.


do not advance clock or clock advances normally.


Add and enable a new scenario. Multiple options are allowed. Scenarios are in $FG_ROOT/AI/.


Enable/disable the AI subsystem. When disabled this also disables showing the models of other multiplayer aircraft.


Enable/disable the autogenerated traffic subsystem.


Open Launcher automatically when exiting the FlightGear.


Load recording of earlier flightgear session. For <name>, if <name> ends with .fgdata it is treated as the local path of the recording file; otherwise we form the local path by prepending <name> with the tape directory and appending ".fgtape". For <url> (starting with http:// or https://) we download the remote recording (which must be a Continuous recording) in the background to a url-dependent filename while replaying it; if the url-dependent filename already exists it is assumed to be a truncated download and we only download any remaining data.


--aircraft=name (--vehicle=name)

Select an aircraft profile as defined by a top level -set.xml.


Specify the exact directory to use for the aircraft (normally not required, but may be useful). Interpreted relatively to the current directory. Causes the <path-cache> from autosave_X_Y.xml, as well as --fg-aircraft options and the FG_AIRCRAFT environment variable to be bypassed.


Print a list of the currently available aircraft types.


Allows you to define a minimum status level (=development status) for all listed aircraft.


Enable/disable auto coordination. Disabled as default. If enabled, the rudder will respond according to the movement of the ailerons.


Select aircraft livery.


Specify the initial state of the aircraft to the given value. The states that can be used depend on the aircraft. For example, the Cessna 172P has only one state: auto.

Flight Model

--fdm={ada | acms | aisim | balloon | jsb | larcsim | magic | network | pipe | ufo | yasim | external | null}

Select the core flight dynamics model.


Select aircraft aerodynamics model to load.


Run the FDM this rate (iterations per second).


Run the FDM 'n' times faster than real time.


Trim or do not attempt to trim the model (only with --fdm=jsbsim).


Start at ground level (default) or in air (implied when using --altitude).

Initial Position and Orientation


Specify airport (e.g. KOAK).


Specify starting runway (must also specify an airport).

--parking-id=name (--parkpos=name)

Specify a gate at the airport (e.g. 747d11).


Specify starting position on an AI carrier.


Specify a starting position relative to the carrier where you can use the predefined abeam (start on downwind abeam) or FLOLS (start on final approach) values, or specify the name of the carrier's parking position. Must also specify a carrier by --carrier.


Specify starting position relative to a VOR.


Specify the frequency of the VOR. Use with --vor=ID.


Specify starting position relative to an NDB.


Specify the frequency of the NDB. Use with --ndb=ID.


Specify starting position relative to a fix.


Specify distance to reference point (nautical miles).


Specify heading to reference point.


Starting longitude (west = -).


Starting latitude (south = -).


Starting altitude (in feet unless --units-meters specified).


Specify heading (yaw) angle (Psi).


Specify roll angle (Phi).


Specify pitch angle (Theta).


Specify initial airspeed in knots or mach number.


Specify flight path angle (can be positive).


Specify initial climb of rate (can be negative).


Specify velocity along the body X axis (in feet unless --units-meters specified).


Specify velocity along the body Y axis (in feet unless --units-meters specified).


Specify velocity along the body Z axis (in feet unless --units-meters specified).


Specify velocity along a South-North axis (in feet unless --units-meters specified).


Specify velocity along a West-East axis (in feet unless --units-meters specified).


Specify velocity along a vertical axis (in feet unless --units-meters specified).

Audio Options


Show a list of available audio device.


Explicitly specify the audio device to use. To get available names use --show-sound-devices.


Enable/disable sound.

Rendering Options


Enable/disable multi sample buffer (anti-aliasing).


Specify number of multi samples (anti-aliasing). Valid values is 2, 4, 8, 16.


Specify a multiplier for the aspect ratio.


Specify the bits per pixel.


Specify the path to XML file for multi-pass rendering. The path is relative to $FG_ROOT (defaults to Compositor/default.)


Enable/disable celestial body growth illusion near the horizon.


Enable/disable runway light distance attenuation.


Enable/disable specular reflections on textured objects.


Enable/disable 2D (flat) cloud layers.


Enable/disable 3D (volumetric) cloud layers.


Enable/disable texture cache (DDS).


Set the DDS texture cache directory to be different than the default location.


Enable/disable fullscreen mode.


Include/exclude random scenery objects (buildings, etc.)


Enable/disable wireframe drawing mode.


Set the fog. The --fog-disable option will turn off the fog, resulting in increased visibility and a decrease in performance (more terrain to render). The --fog-fastest option will enable fog rendering in a less realistic way, but improving performance. By default, the --fog-nicest option is used to render a realistic fog, at the expense of performance. These options are deprecated.


Specify field of view angle.


Specify window geometry/resolution (640x480, etc).


Specify the materials file used to render the scenery (default: Materials/regions/materials.xml).


Maximum frame rate in Hz.


Enable smooth or flat shading. These options are deprecated.


Specify anisotropic filtering of terrain textures. Valid values is 1, 2, 4, 8, 16. Default is 1.


Specify the default forward view direction as an offset from straight ahead. Allowable values are LEFT, RIGHT, CENTER, or a specific number in degrees.


Specify the terrain engine you want to use: tilecache or pagedLOD.


Specify the detail levels, where levels are a space-separated numeric list of levels. The default is "1 3 5 7 9". Use with --terrain-engine=pagedLOD.


Specify the resolution of the terrain grid. Defaults is 1. Use with --terrain-engine=pagedLOD.


Specify the method of texturing the terrain. The default is bluemarble. Use with --terrain-engine=pagedLOD.


Specify the range multiplier (point from low to fine detail). Defaults is 2. Use with --terrain-engine=pagedLOD.


Enable summer season or winter - default summer.

Hud Options


Enable/disable Heads Up Display (HUD).


Enable/disable anti-aliased HUD.


Enable/disable 3D HUD.


Hud displays number of triangles rendered or percentage of triangles culled.

Time Options

The following time and date setting options are not compatible with each other, so only one of them should be given.


Specify a time of day.


Add this time offset to --time-match-real.


Synchronize time with current time at chosen airport.


Synchronize time with system time of computer.


Specify a starting date/time with respect to system time.


Specify a starting date/time with respect to Greenwich Mean Time.


Specify a starting date/time with respect to Local Aircraft Time.

Network Options


Specify the proxy server and port to be used. Username and password are optional. If present, they should be listed as MD5 hashes. This option is only useful when --real-weather-fetch is enabled.


Enable HTTP server on the specified port.

--telnet={port|socket,bi,hz,localhost,port,tcp} (--props={port|socket,bi,hz,localhost,port,tcp})

Enable telnet server on the specified port. Optionally, you can change the hz (number of packets per second).


Enable screen shot HTTP server on the specified port. This option has been withdrawn, instead use --httpd and /screenshot URL.


Remove security flag, which means that network connections will be allowed full access to the simulator including running arbitrary scripts. Ensure you have adequate security such as a firewall which blocks external connections.


Enable/disable crash and error reports from being sent to the development team for analysis.

MultiPlayer Options


Assign a unique name to a player. A call sign must be at most 10 characters long and can only contain numbers, letters of the English alphabet, hyphens (-) and underscores (_). Longer call signs are truncated, and characters that do not match those listed above are replaced with hyphens.


Specify multipilot communication settings. Multiple instances can be used.


Enable/disable built-in FGCom (voice communication with ATC.)


In multiplayer mode, when you select an initial position on the runway, you will be moved by default to the hold-short position, which is on the taxiway, just in front of the runway. The --disable-hold-short option allows you to disable this behavior, but keep in mind that this is undesirable, as it may interfere with others taking off or landing.

Route/Way Point Options


Specify a waypoint for the GC autopilot. Multiple instances can be used.


Read all waypoints from a file.

IO Options


Open connection using a predefined communication interface and a preselected communication protocol.


Open connection using the Atlas protocol.


Open connection using the ATC sim protocol (atc610x).


Emit the Garmin AV400 protocol required to drive a Garmin 196/296 series GPS.


Emit the set of AV400 strings required to drive a Garmin 400-series GPS from FlightGear.

--AV400WSimA=params, --AV400WSimB=params

The Garmin WAAS GPS uses 2 serial channels to communicate with the simulator. These 2 channels are represented by the FGAV400WSimA and the FGAV400WSimB classes. The "A" channel is similar to the previous AVSim400 protocol. The "B" channel is considered the "GPS" channel and uses a different protocol than the "A" channel. The GPS unit expects input on the "B" channel at two different frequencies (1hz and 5hz, normally). The "B" channel also expects responses to certain output messages.


Open connection using the FLARM protocol, which includes NMEA/GPS and traffic reporting messages.


Open connection using the Garmin GPS protocol.


Open a remote connection using the HLA protocol. Currently, this option is disabled.


Open a local connection using the HLA protocol. Currently, this option is disabled.


Open connection using the International Gliding Commission (IGC) protocol.


Open connection to an Agwagon joystick.


Open connection to a remote joystick.


Open connection using the FG Native protocol.


Open connection using the FG Native Controls protocol.


Open connection using the FG Native FDM protocol.


Open connection using the FG Native GUI protocol.


Open connection using the NMEA protocol.


Open connection using the OpenGC protocol.


Open connection using the interactive property manager (same as --telnet).


Open connection using the PVE protocol (ProVision Entertainment - some sort of motion platform).


Open connection using the Ray Woodworth motion chair protocol.


Open connection using the RUL protocol (some sort of motion platform some guy was building).

Under Windows, you must use a special escape sequence if you need to specify a COM port higher than 9.

Example: --generic=\\.\COM10,out,1,/tmp/data.xml,myproto

This is per the Microsoft KB article here:

Avionics Options

--com1=frequency, --com2=frequency

Set the COM1 and COM2 radio frequency.

--nav1=[radial:]frequency, --nav2=[radial:]frequency

Set the NAV1 and NAV2 radio frequency, optionally preceded by a radial.

--adf1=[rotation:]frequency, --adf2=[rotation:]frequency

Set the ADF1 and ADF2 frequency to frequency kHz. You can optionally specify the rotation angle of its compass card by prefixing the frequency with the angle and a colon. The --adf option is deprecated.


Slave the ADF to one of the NAV radios, or set its internal frequency.

Environment Options


Enable/disable METAR based real weather fetching. Enable requires an open internet connection.


Enable/disable celestial body growth illusion near the horizon.


Specify initial visibility in meters or in statute miles. It works only with Basic Weather.


Specify the direction from which the wind is blowing (DIR in degrees) and its SPEED (in knots). If the wind direction is variable, specify the range as DIR:MAXDIR, as a minimum and maximum angle in degrees. If you want the simulator to also model wind gusts, set the maximum :GUST rate in knots.


Specify turbulence where value must to be from 0.0 (calm) to 1.0 (severe).


Create an overcast ceiling, optionally with a specific thickness (defaults to 2000 ft). This option looks like it has been broken for a long time and doesn't work at all.


Set up random wind direction and speed.

--metar="metar string"

Starts with a certain METAR string. Only works if live weather is disabled.

Situation Options


Fail the pitot, static, vacuum, or electrical system (repeat the option for multiple system failures).

Debugging Options

--console (-c)

Display console (Windows specific).


Enable developer mode which will log more events.


Abort on encountering a floating point exception.

--fgviewer file

Use a model viewer rather than load the entire simulator.


Print a report in JSON format on the standard output. The report will give useful information for debugging purposes, such as the FlightGear version, the scenery/aircraft paths in use, the TerraSync and the data download directories and the paths to navigation data files.


Set the logging level for this session. 0 = verbose, 5 = alerts only. See also Commonly used debugging tools#fgfs.log.

--log-class={none|ai|aircraft|astro|atc|autopilot|clipper|cockpit| environment|event|flight|general|gl|gui|headless|input|instrumentation| io|math|nasal|navaid|network|osg|particles|sound|systems|terrain| terrasync|undefined|view|all}

Specify which logging class(es) to use.


Save the logs in the given directory. If desktop is entered instead of the path, the logs are saved on the Desktop. This option may be given several times, using a different directory each time. Inside the specified directory, the log file will be named FlightGear_YYYY-MM-DD_num.log, where YYYY-MM-DD is the current date and num is a progressive number starting at 0.


Trace the reads for a property; multiple instances can be used.


Trace the writes for a property; multiple instances can be used.


Remove $FG_HOME directory. For Windows, it additionally removes TerraSync, Aircraft and TextureCache directories from download directory.

Related content

Wiki articles

Source files