NASA astronaut Joe Engel, who served as a backup pilot for the Apollo 14 mission and then later commanded the space shuttle Discovery in 1985, died at the age of 91 on July 10. (Photo courtesy of NASA)

July 11 (UPI) -- Friends, family and former colleagues are mourning the death of retired astronaut Joe Engel, 91, who died in his Houston home on Wednesday, NASA announced.

Engel was a U.S. Air Force major general and the only astronaut to pilot both the X-15 experimental aircraft and the space shuttle.

"A natural pilot, Gen. Joe Engle helped humanity's dreams take flight -- in the X-15 program, the Apollo Program and as one of the first commanders in the Space Shuttle Program," NASA Administrator Bill Nelson said in a statement.

"He was one of the first astronauts I met at NASA's Johnson Space Center in Houston. I'll never forget his big smile, his warmth and his courage. We all will miss him."

Engel's tenure reached back as far as the Apollo program in 1977, when he served as a backup pilot for the Apollo 14 mission, and then commanded the space shuttle Discovery in 1985, which was known as one of NASA's most challenging missions.

The Discovery crew deployed three commercial satellites, then retrieved, repaired and redeployed another malfunctioning satellite that had been launched on a previous shuttle mission.

"As we mourn the immense loss of Joe, we're thankful for his notable contributions to the advancement of human spaceflight," said Vanessa Wyche, director at the NASA Johnson Space Center. "Joe's accomplishments and legacy of perseverance will continue to inspire and impact generations of explorers for years to come."

Engel acquired a lot of significant numbers as a pilot and an astronaut. He logged more than 14,000 flight hours as a jet pilot, 224 hours in space and flew more than 180 different types of aircraft over his career.

He earned his pilot wings in 1958 and was selected as an astronaut at the age of 32 after an already successful and respected career as a highly decorated and awarded Air Force pilot.

Engel was born in Chapman, Kan., in 1932, and graduated from the University of Kansas with a degree in aeronautical engineering in 1955.

"Joe Henry was a loving husband, father and grandfather. Blessed with natural piloting skills, Gen. Joe, as he was known to many, was at his happiest in any cockpit. Always with a smile, he lived a fulfilled life as a proud American, U.S. Air Force pilot, astronaut and Kansas Jayhawk," his wife, Jeanie, said in the NASA statement.

"His passing leaves a tremendous loss in our hearts. We take comfort that he has joined Tom Stafford and George Abbey, two of the best friends anyone could ask for."

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