Astronaut John Glenn (right) undergoing training. (NASA)
Astronaut John H. Glenn Jr., undergoes a simulated orbital flight in the Manned Spacecraft Center's procedure trainer at Langley Air Force Base, Virginia, Nov. 29, 1961. (NASA)
Astronaut John H. Glenn Jr. in his Mercury flight suit. (NASA)
Astronaut John H. Glenn Jr. in a silver Mercury pressure suit in preparation for launch. On Feb. 20, 1962, Glenn lifted off into space aboard his Mercury Atlas (MA-6) rocket and became the first American to orbit the Earth. (NASA)
Astronaut John Glenn in space during his flight on Friendship 7. Glenn was in a state of weightlessness traveling at 17,500 mph as these pictures were taken. (NASA)
Astronaut John H. Glenn Jr., pilot of the Mercury-Atlas 6 spaceflight, aboard the U.S.S. Randolph after his Earth-orbital mission. (NASA)
Mercury astronauts John H. Glenn Jr., Virgil I. Grissom and Alan B. Shepard Jr. standing by the Redstone rocket. (NASA)
Sen. John Glenn, D-Ohio (U.S. Senate)
John Glenn in a flight suit around the time of the STS-95 Discovery mission in 1998. (NASA)
Space Shuttle Discovery shoots into the sky carrying a crew of six, including Payload Specialist John H. Glenn Jr., senator from Ohio, who is making his second voyage into space after 36 years. (NASA)
Payload Specialist John Glenn works with the Osteporosis Experiment in Orbit on shuttle Discovery, Nov. 18, 1998. (NASA)
Orbiter Discovery prepares to land at the Shuttle Landing Facility, Nov. 7, 1998. Payload Specialist John H. Glenn Jr., a senator from Ohio, is on board. (NASA)
President Barack Obama meets with former Sen. John Glenn, D-Ohio, in the Oval Office, to discuss the president's plan for a space program, July 19, 2010. (White House)
President Barack Obama presents former Marine Corps pilot, NASA astronaut, and U.S. Sen. John Glenn with the Medal of Freedom at the White House, May 29, 2012. (NASA)
Former Marine, astronaut, and U.S. Sen. John Glenn lies in repose, under a U.S. Marine honor guard, in the Rotunda of the Ohio Statehouse in Columbus, December 16, 2016. (NASA)
U.S. Marines carry in the casket of former Marine, astronaut, and U.S. Sen. John Glenn during a ceremony to celebrate his life at The Ohio State University in Columbus, December 17, 2016. (NASA)
Gen. Robert B. Neller, the commandant of the Marine Corps, salutes during the funeral for retired Marine Col. John H. Glenn Jr. at the Old Post Chapel, Arlington, Va., April 6, 2017. (U.S. Marine Corps)
A horse-drawn caisson carries former astronaut and U.S. Senator John Glenn to his final resting place during the interment ceremony at Arlington National Cemetery, April 6, 2017, in Virginia. (NASA)
A horse-drawn caisson carries former astronaut and U.S. Senator John Glenn to his final resting place during the interment ceremony at Arlington National Cemetery, April 6, 2017, in Virginia. (NASA)
The caisson carrying the remains of retired Marine Col. John H. Glenn Jr. at Arlington National Cemetery, Arlington, Va., April 6, 2017. (U.S. Marine Corps)
Marine Corps pallbearers carry former astronaut and U.S. Sen. John Glenn to be laid to rest at Arlington National Cemetery in Virginia, April 6, 2017. (NASA)
Marine Sgt. Christian Rangeo plays "Taps" during the funeral service for John Glenn, who was buried with full military honors, at Arlington National Cemetery in Virginia, April 6, 2017. (NASA)
Gen. Robert B. Neller, the commandant of the Marine Corps, presents a U.S. flag to Annie Glenn, wife of retired Col. John Glenn, during his funeral at Arlington National Cemetery, April 6, 2017. (NASA)
Gen. Robert B. Neller, the commandant of the Marine Corps, presents a U.S. flag to David Glenn, son of John Glenn, during a graveside interment ceremony at Arlington National Cemetery, April 6, 2017, in Virginia. (NASA)
U.S. Army Soldiers with caisson platoon, 1st Battalion, 3rd United States Infantry Regiment, ride their horses through Arlington National Cemetery for the funeral for retired Marine Col. John Glenn, Arlington, Va., April 6, 2017. (U.S. Marine Corps)