Prolific NASA astronaut Mike Fincke has announced his retirement from the U.S. space agency after 30 years of public service. NASA announced Fincke's decision on Wednesday (Aug. 12), celebrating his contributions to spaceflight and long career of accomplishments. “Few people have had the opportunity to shape as many chapters of NASA’s history as Mike Fincke,” NASA Administrator Jared Isaacman said that day in a statement. Fincke departs as NASA's fourth-most flown astronaut, racking up a cumulative 549 days in space over four separate spaceflights. During those, he performed nine spacewalks and served twice as commander of the International Space Station (ISS). Most recently, he launched as pilot on SpaceX's Crew-11 mission to the ISS, stepping into the role of commander for ISS Expedition 74 from August 2025 to January 2026. Before his acceptance into NASA's 16th astronaut class in 1996, Fincke earned two bachelor's degrees from the Massachusetts Institute of Technology (MIT), in aeronautics and astronautics as well as Earth science, atmospheric and planetary sciences. Following his time at MIT, he did a summer stint at the Moscow Aviation Institute and later earned master's degrees in aeronautics and astronautics, and in planetary geology from Stanford and the University of Houston-Clear Lake, respectively. Fincke also served in the U.S. Air Force prior to his career at NASA. He graduated from the U.S. Air Force Test Pilot School in 1994, then was assigned as a space systems engineer and flight test engineer at Edwards and Eglin Air Force bases in California and Florida, respectively. Those stints were followed by his role as U.S. flight-test liaison for the Japanese-U.S. XF-2 fighter program in Japan.Following his two years of astronaut-candidate training, Fincke was assigned to NASA's Astronaut Office Station Operations Branch's Crew Test Support Team in Russia. There, he served as ISS CAPCOM (Spacecraft Communicator) and ISS crew procedures team lead until he began official spaceflight training in 1999.His first rocket launch was aboard the Soyuz TMA-4 mission to the ISS in 2004, where he served as science officer and flight engineer for Expedition 9 and completed four EVAs (extravehicular activities, or spacewalks). Fincke's second launch brought him back to the ISS in 2008, as a member of Soyuz TMA-13. It was then that Fincke took command of the space station for the first time. As Expedition 18 commander, Fincke added two more EVAs to his career total and oversaw the preparation of ISS facilities to begin supporting an increase from three-person to six-person crews. Fincke was also aboard for the final launch of NASA's space shuttle Endeavour on the STS-134 mission in 2011, which returned him to the ISS for a third time. As mission specialist and robotic-arm operator, he supported the installation of the space station's dark-matter-hunting Alpha Magnetic Spectrometer (AMS) instrument, and performed three additional EVAs that marked the official completion of ISS orbital assembly and were the last-ever spacewalks by a space shuttle crew. By 2014, Fincke was serving as chief of the Astronaut Office’s Commercial Crew Branch, where he played a key role in the development and testing of the SpaceX Crew Dragon and Boeing Starliner spacecraft. In January 2019, he was assigned to Boeing’s Crew Flight Test (CFT) mission as joint operations commander, and he remained on the prime crew until June 2022, when he transitioned to the CFT backup crew.Mike Fincke is helped off SpaceX's Crew Dragon after Crew-11 splashdown in the Pacific Ocean on Jan. 15, 2026. (Image credit: NASA/SpaceX)Fincke's most recent mission, Crew-11, launched to the ISS in August 2025. It was the second time he was appointed commander of the space station, this time for Expedition 74, but his stint, and that of the other Crew-11 astronauts, was cut short due to an unexpected medical issue. Leading up to what would have been his 10th career EVA, NASA abruptly canceled spacewalk prep by Fincke and fellow NASA astronaut Zena Cardman after a "medical concern" arose that took priority over the planned station maintenance. Though not considered an emergency, the episode was deemed serious enough for NASA to return the Crew-11 astronauts to Earth earlier than expected, and Fincke and his fellow crewmates safely splashed down in the Pacific Ocean aboard their SpaceX Crew Dragon a week later. During the mission, NASA did not reveal the afflicted astronaut's name and condition, citing privacy concerns. A little more than a month after Crew-11's return, however, NASA and Fincke revealed that he was the crew member who experienced the medical issue, which he later described as a temporary inability to speak, according to an Associated Press report. Fincke fully recovered from the episode and is now in good health.“Mike approached every assignment with experience, humility, and an unwavering focus on the mission,” said Scott Tingle, chief of NASA's Astronaut Office, in the agency's announcement. “Whether flying aboard the station, supporting crews from the ground, or helping shape the spacecraft that future crews will rely on, he consistently strengthened our team. His legacy is woven into the way we fly today.”NASA did not indicate if Fincke plans to continue his involvement with the space industry through the private sector, but did highlight his dedication to support humanity's drive to explore the cosmos. "I remain deeply committed to the work of exploration," Fincke said in the statement. “NASA gave me the extraordinary privilege of serving alongside remarkable people, flying and helping develop spacecraft, and contributing to the International Space Station from its earliest days through command in orbit … I am excited to carry those lessons forward and help prepare the next generation of engineers, explorers, and leaders."