Peggy Whitson floats in the Cupola aboard the International Space Station. The record-setting NASA astronaut retired from the space agency on June 15, 2018.

The United States' most experienced space flier is hanging up her wings.

Astronaut Peggy Whitson, who has spent more time in space than any other American, retired from NASA today (June 15), agency officials announced.

"Peggy Whitson is a testament to the American spirit," NASA Administrator Jim Bridenstine said in a statement. "Her determination, strength of mind, character, and dedication to science, exploration, and discovery are an inspiration to NASA and America. We owe her a great debt for her service, and she will be missed. We thank her for her service to our agency and country." [In Photos: Record-Breaking NASA Astronaut Peggy Whitson]

Iowa native Whitson, 58, earned a doctorate in biochemistry from Rice University in 1985. She went to work at NASA's Johnson Space Center in Houston a year later, as a National Research Council resident research associate.

Whitson filled several scientific posts at the agency over the next decade — including project scientist for the Shuttle-Mir Program and co-chair of the U.S.-Russian Mission Science Working Group — and was then chosen for the astronaut corps in 1996.

Whitson flew three missions aboard the International Space Station (ISS): Expedition 5 in 2002; Expedition 16 in 2008, during which she became the first female commander of the orbiting lab; and an extended stint from November 2016 through September 2017, which spanned Expeditions 50, 51 and 52. Whitson also commanded Expedition 51, becoming the first woman to lead an ISS mission twice.

During her career, Whitson racked up a total of 665 days in space — more than any other NASA astronaut, and a record for women worldwide. (A handful of male Soviet/Russian cosmonauts have spent more time in space, including Gennady Padalka, who holds the world mark of 878 days.)

Whitson also has performed more spacewalks than any other woman, venturing outside the ISS on 10 occasions for a record-setting total of 60 hours and 21 minutes. And during her most recent trek to the ISS, Whitson became the oldest female astronaut (57) to reach orbit.

She set some records on the ground as well, becoming the first woman (and first nonmilitary person) to serve as chief of NASA's astronaut corps. She held this position from 2009 through 2012.

"Peggy is a classmate and a friend, and she will be deeply missed," Pat Forrester, the current chief of the Astronaut Office, said in the same statement. "Along with her record-setting career, she leaves behind a legacy of her passion for space."

You can learn more about Whitson and her extraordinary spaceflight career in her NASA biography.

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