Joe Lengyel was commissioned through the Air Force ROTC Program at North Texas State University on December 21, 1981, and went on active duty beginning in March 1982. Lengyel completed Undergraduate Pilot Training and was awarded his pilot wings at Laughlin AFB, Texas, in February 1983. After completing Lead-in Fighter Training and F-16 Upgrade Training, he served as an instructor pilot at Nellis AFB, Nevada, from January 1984 to April 1986. Capt Lengyel next served as an instructor pilot and flight examiner at Kunsan AB, South Korea, from April 1986 to March 1987, and then attended F-16C Conversion Training at Luke AFB, Arizona, from May to June 1987. From June 1987 to August 1991, he served as an instructor pilot and Chief of Weapons for the 512th Tactical Fighter Squadron of the 86th Tactical Fighter Wing at Ramstein AB, Germany. Maj Lengyel joined the Texas Air National Guard in September 1991, and served with the 182nd Fighter Squadron at Kelly AFB, Texas, from September 1991 to November 1995. From November 1995 to April 1997, he served as Commander of the 149th Operations Support Flight of the 149th Operations Group at Kelly, and then became Operations Officer of the 182nd Fighter Squadron, where he served until October 1998. Col Lengyel then became Commander of the 182nd Fighter Squadron, serving until October 1999, when he became Commander of the 149th Operations Group at Lackland AFB, Texas. In March 2002, Lengyel was made Vice Commander of the 149th Fighter Wing at Lackland, where he served until May 2004. He was Commander of the 455th Expeditionary Operations Group at Bagram AB, Afghanistan, from June to September 2004, and then served as Air National Guard Advisor to the Commander in Chief, U.S. Air Forces in Europe, from October 2004 to October 2006. Col Lengyel was Commander of the Air National Guard Readiness Center at Andrews AFB, Maryland, from September 2006 to September 2008, and then served as Deputy Director of the Air National Guard at Andrews AFB from September 2008 to June 2009. His next assignment was as Military Assistant Deputy Chief of Staff for Strategic Plans and Programs with Headquarters U.S. Air Force at the Pentagon from June 2009 to July 2010, followed by service as Vice Commander of 1st Air Force at Tyndall AFB, Florida, from July 2010 to June 2011. Gen Lengyel served as the Senior U.S. Defense Official, Chief of the Office of Military Cooperation, and Defense Attache with U.S. Central Command in Cairo, Egypt, from June 2011 to August 2012, and then as Vice Chief of the National Guard Bureau at the Pentagon from August 2012 to August 2016. His final assignment was as Chief of the National Guard Bureau at the Pentagon from August 2016 until his retirement from the Air Force on August 3, 2020. He is a Command Pilot with more than 3,000 flying hours, mostly in the F-16 Fighting Falcon.

His Air Medal Citation reads:

Major Joseph L. Lengyel distinguished himself by meritorious achievement while participating in sustained aerial flight as an F-16C Aircraft Commander, 4406th Operations Group (Provisional), Ahmed Al Jaber Air Base, Kuwait, from 29 March 1997 to 30 April 1997. During this period, Major Lengyel flew combat missions into Iraq in support of Operation SOUTHERN WATCH with a one hundred percent effectiveness record. His participation in air interdiction, close air support, and counter-air missions served to enforce the United Nations Security Council resolutions restricting Iraq air and ground operations south of the 33rd parallel in southern Iraq. These flights were flown with live ordnance loaded fighters performing targeting and navigational familiarization within the hostile fire environment of Iraq. These missions involved direct exposure to threat aircraft, radar, and surface-to-air missiles. Participation in this United Nations mission further supported the United States military presence throughout Iraq, Saudi Arabia, Kuwait, and the Arabian Gulf. His devotion and selfless dedication to the tasked sorties ensured operational success and mission effectiveness. The professional ability and outstanding aerial accomplishments of Major Lengyel reflect great credit upon himself, the Air National Guard, and the United States Air Force.