LD Johnston was born on April 28, 1947, in Oklahoma City, Oklahoma. He was commissioned a 2d Lt in the U.S. Air Force through the Air Force ROTC program at Oklahoma State University on January 18, 1970, followed by Undergraduate Pilot Training from February 1970 to February 1971. Lt Johnston completed F-4 Phantom II Combat Crew Training in September 1971, and then served as an F-4 pilot and fast forward air controller with the 388th Tactical Fighter Wing at Korat Royal Thai AFB, Thailand, from October 1971 to October 1972. His next assignment was as an F-4 instructor pilot with the 35th Tactical Fighter Wing at George AFB, California, from November 1972 to December 1975, followed by service as an F-4 fighter weapons instructor, flight commander, and then Chief of Wing Weapons and Tactics with the 347th Tactical Fighter Wing at Moody AFB, Georgia, from December 1975 to July 1978. Capt Johnston served as a fighter weapons instructor and Chief of Weapons Training with the 406th Tactical Fighter Wing at Zaragoza AB, Spain, from July 1978 to December 1979, and then as a Staff Action Officer with Headquarters U.S. Air Forces in Europe at Ramstein AB, West Germany, from January 1980 to August 1981. He attended Air Command and Staff College at Maxwell AFB, Alabama, from August 1981 to June 1982, followed by service as Chief of Wing Weapons and Tactics, Assistant Operations Officer, Operations Officer, and then as an F-16 Fighting Falcon Squadron Commander with the 474th Tactical Fighter Wing at Nellis AFB, Nevada, from June 1982 to January 1987. Col Johnston next served as Director of Assignments with Headquarters Tactical Air Command at Langley AFB, Virginia, from January 1987 to July 1989, and he then attended Naval War College at Newport, Rhode Island, from August 1989 to June 1990. His next assignment was as Commandant of the U.S. Air Force Fighter Weapons School at Nellis AFB from July 1990 to April 1991, followed by service as Vice Commander of the 363rd Fighter Wing at Shaw AFB, South Carolina, from April 1991 to March 1993. He served as Vice Commander and then Commander of the Army-Air Force Center for Low Intensity Conflict at Langley AFB from March 1993 to March 1995, and then as Commander of the 8th Fighter Wing at Kunsan AB, South Korea, from March 1995 to March 1996. Gen Johnston's next assignment was as Commander of the 347th Wing at Moody AFB, Georgia, from April 1996 to July 1998, followed by service as Director of Plans and Programs with Headquarters Air Combat Command at Langley AFB from July 1998 to January 2000. His final assignment was as Commander of the Air Warfare Center at Nellis AFB from January 2000 until his retirement from the Air Force on August 1, 2002.

His 4th Distinguished Flying Cross w/Valor Citation reads:

First Lieutenant Lawrence D. Johnston distinguished himself by heroism while participating in aerial flight as an F-4E Aircraft Commander in Southeast Asia on 15 September 1972. On that date, despite the presence of numerous attacking hostile interceptor aircraft, extremely heavy antiaircraft artillery fire, and the incomparable hazard of single-ship operation in the Hanoi-Haiphong area, Lieutenant Johnston executed an attack on two active surface-to-air missile sites that threatened ingressing and egressing strike forces. With complete disregard for his own safety, Lieutenant Johnston skillfully executed precise expenditure of ordnance against these heavily defended sites, inflicting major damage to the installations and providing invaluable protection for other allied fighter-bombers. The outstanding heroism and selfless devotion to duty displayed by Lieutenant Johnston reflect great credit upon himself and the United States Air Force.