The camera is controlled using the mouse and keyboard, or by using an attached joystick or gamepad after you set the control assignments. There are three control modes: Free mode, Spacecraft mode, and Aircraft mode. These can be toggled by pressing keys , , and  respectively. The camera in Free mode has no inertia, whereas Spacecraft mode and Aircraft mode have inertia.
Free mode is the default mode, but can also be set by using the  key. The controls are similar to a First-Person Shooter game, using the [W] [A] [S] [D] [R] [F] keys + Mouse to control the orientation and movement of the camera.
To rotate the camera (up, down, left and right) press the [Left mouse button] (LMB) and drag the mouse. To rotate counter-clockwise around the camera's longitudinal axis (view axis), press [E], and for clockwise press [Q]. Rotation can also be controlled using the numeric keypad:  and  for up and down,  and  for left and right, and  and  for clockwise and counter-clockwise. The [Num Lock] key does not affect these controls at all.
To move forward press [W], the camera will then accelerate forward. To move backward, press [S]; to move left, press [A]; to move right, press [D]; to move up, press [R]; and to move down, press [F]. To stop anytime, just release the movement keys. Movement can also be controlled by using the arrow keys: The [Up] and [Down] keys controls movement forward and backward, and [Left] and [Right] move to the left and right. Movement up and down can be controlled by the  and  keys on the numeric keypad.
To increase flight speed, press and hold the [+] on the numeric keypad or [=] on the main keyboard. To reduce speed, press and hold the [-] key. Your current speed is displayed at top center of the screen, but only when speed is being changed. Speed information is also displayed permanently at the bottom left of the screen. Changing velocity gradually can be controlled by scrolling the Mouse wheel up and down. To increase or decrease speed rapidly press [+] or [-] while holding down the [Ctrl] key. You can also use [Ctrl] + [Mouse wheel]. These speed increases can be incrementally preset; for example: 1 km/s to 3 km/s, 10 km/s, etc. They can also be customized from the config/user.cfg file.
Spacecraft mode can be set by using the  key. In this mode the camera's behavior resembles a rigid body in zero gravity: the camera maintains its linear and angular velocity in the absence of keyboard and mouse input; therefore the camera's absolute direction of motion does not depend upon the orientation of the camera.
Pressing a movement key (as described in Free mode above) accelerates the camera in that direction. The rate of acceleration can be changed by using the [+] and [-] keys or the [Mouse wheel] as explained in detail in Free Mode above.
[Mouse drag] + [LMB] causes the camera to angularly (rotationally) accelerate. The acceleration is proportional to the magnitude of the mouse shift. Pressing the rotation keys ( [Q], [E] and , , , , ,  on the numeric keypad) defines a fixed angular acceleration. Releasing [LMB] turns off acceleration, and the camera will continue to rotate at a constant rate. To stop moving completely, press [Z]; to stop rotating press [X], or  on the numeric keypad.
Aircraft mode can be set by pressing the  key. This mode is similar to Spacecraft mode in that movement and rotation rates remain constant, while the control keys and mouse accelerate the camera's linear and angular velocity (movement and rotation). However, unlike in Spacecraft mode, the camera's direction of movement is synced to its orientation. If you accelerate forward, then rotate the camera, the camera will continue to move in the direction that you rotated it to. Giving the camera the right forward speed with the [W] key allows you to use this mode somewhat like a flight simulator, changing flight direction by rotating the camera. [Z] and [X] are used to stop the camera's movement and rotation, like in Spacecraft mode.
When the camera collides with a planetary surface, its motion will be canceled to prevent penetration of the surface. If the camera's velocity is greater than 1 km/s when collision occurs, its velocity will reset to 20-30 m/s to prevent flying too fast over the surface.
Some commands are also available on the lower-left toolbar.