Question: Which United States Marine Corps aviator preceded United States Navy Commander Scott Carpenter as one of the first Americans in space?
Context: James F. "Jim" Amos (born November 12, 1946) is a retired United States Marine Corps four-star general who served as the 35th Commandant of the Marine Corps.  As a Naval Aviator, Amos commanded the 3rd Marine Aircraft Wing during the Iraq War in 2003 and 2004.  He served as the 31st Assistant Commandant of the Marine Corps.  He is the first Marine Corps aviator to serve as commandant. USS "Frank E. Petersen Jr." (DDG-121) is a planned United States Navy "Arleigh Burke"-class Flight IIA guided missile destroyer, the 71st overall for the class.  The ship was named for United States Marine Corps Lieutenant General Frank E. Petersen Jr. (March 2, 1932 – August 25, 2015), the first African-American Marine Corps aviator and the first African-American Marine Corps general.  The contract for the ship, along with the name, was first announced in a press release from Huntington Ingalls Industries on 30 March 2016. Frank Emmanuel Petersen Jr. (USMC) (March 2, 1932 – August 25, 2015) was a United States Marine Corps lieutenant general.  He was the first African-American Marine Corps aviator and the first African-American Marine Corps general. Ross Erastus Rowell (22 September 1884 – 6 September 1947) was a highly decorated United States Marine Corps aviator who achieved the rank of lieutenant general by the end of his 40 years of service.  He served as Director of Marine Corps Aviation from May 30, 1935 until March 10, 1939 and was one of the three senior officers of Marine Corps aviation during World War II. Richard C. Mangrum (October 27, 1906 – September 28, 1985) was a United States Marine Corps lieutenant general who served as Assistant Commandant of the Marine Corps from 1965 to 1967.  Mangrum was a Marine Corps aviator who was awarded the Navy Cross and the Distinguished Flying Cross for his actions during the Guadalcanal Campaign in World War II. Lieutenant Colonel Alfred Austell Cunningham (March 8, 1882 – May 27, 1939) was a United States Marine Corps officer who became the first Marine Corps aviator and the first Director of Marine Corps Aviation.  His military career included service in the Spanish–American War, World War I, and U.S. operations in the Caribbean during the 1920s. The Commandant of the Marine Corps (CMC) is normally the highest-ranking officer in the United States Marine Corps and is a member of the Joint Chiefs of Staff.  The CMC reports directly to the United States Secretary of the Navy and is responsible for ensuring the organization, policy, plans, and programs for the Marine Corps as well as advising the President, the Secretary of Defense, the National Security Council, the Homeland Security Council, and the Secretary of the Navy on matters involving the Marine Corps.  Under the authority of the Secretary of the Navy, the CMC designates Marine personnel and resources to the commanders of Unified Combatant Commands.  The Commandant performs all other functions prescribed in Section 5043 in Title 10 of the United States Code or delegates those duties and responsibilities to other officers in his administration in his name.  As with the other joint chiefs, the Commandant is an administrative position and has no operational command authority over United States Marine Corps forces. Malcolm Scott Carpenter (May 1, 1925 – October 10, 2013), (Cmdr, USN), was an American naval officer and aviator, test pilot, aeronautical engineer, astronaut, and aquanaut.  He was one of the original seven astronauts selected for NASA's Project Mercury in April 1959.  Carpenter was the second American (after John Glenn) to orbit the Earth and the fourth American in space, following Alan Shepard, Gus Grissom, and Glenn. Avery Raymond Kier (February 11, 1905 – August 7, 1987) was a United States Marine Corps aviator and general officer.  During World War II he served as the commanding officer of VMSB-234 and towards the end of the war was a pioneer in the development of close air support for ground combat operations serving at both Iwo Jima and Okinawa.  Following WW II, Kier served as the commanding officer of numerous Marine aircraft groups, air stations and air wings, with his last assignment being that of Deputy Commander for Fleet Marine Force, Pacific.  He retired from the Marine Corps on 1 March 1967. John Herschel Glenn Jr. (July 18, 1921 – December 8, 2016) was a United States Marine Corps aviator, engineer, astronaut, and United States Senator from Ohio.  In 1962 he became the first American to orbit the Earth, circling it three times.
Answer: John Glenn