901 // get Aircraft running altitude

   901 /**

   902  * Gets the cruise altitude of an aircraft.

   903  * The cruise altitude is determined by the velocity of the vehicle

   904  * and the direction it is moving

   905  * @param v The vehicle. Should be an aircraft

   906  * @returns Altitude in pixel units

   907  */

   904 	switch (v->max_speed) {

   910 	/* Make sure Aircraft fly no lower so that they don't conduct

   905 		case 37: return 162;

   911 	 * CFITs (controlled flight into terrain)

   906 		case 74: return 171;

   912 	 */

   907 		default: return 180;

   913 	byte base_altitude = 150;

   908 	}

   914 

   915 	/* Make sure eastbound and westbound planes do not "crash" into each

   916 	 * other by providing them with vertical seperation

   917 	 */

   918 	switch (v->direction) {

   919 		case DIR_N: case DIR_NE: case DIR_E: case DIR_SE: base_altitude += 15; break;

   920 		default: break;

   921 	}

   922 

   923 	/* Make faster planes fly higher so that they can overtake slower ones */

   924 	base_altitude += min(30 * (v->max_speed / 37), 90);

   925 

   926 	return base_altitude;