NASA officials say Christina Koch on Saturday broke the 288-day record set by former space station commander Peggy Whitson.
The 40-year-old electrical engineer from Montana has been in space since March 15.
She is expected to spend about 11 months on board the International Space Station, falling short of astronaut Scott Kelly's 340-day U.S. record.
A Russian cosmonaut holds the world record at 15 months on a single mission aboard the former Mir space station in the mid-1990s.
NASA tweeted "It's a new day. It's a new dawn," and shared space photos on twitter.
It’s a new day. It’s a new dawn.— NASA (@NASA) December 28, 2019
Today @Astro_Christina sets a record for the longest single spaceflight by a woman, eclipsing the record of 288 days set by @AstroPeggy. #CongratsChristina on reaching new heights! https://t.co/tJSKp9JwbB pic.twitter.com/ZIEPIsZ5SV
The International Space Station wished Koch congratulations on the new record in this tweet:
Students and professors from @NCSSM and @NCState, @Astro_Christina’s alma mater, are saying #CongratsChristina today as she sets a new record for the longest single spaceflight by a woman. pic.twitter.com/cmUtq0xhw3— Intl. Space Station (@Space_Station) December 28, 2019
ABC7 News contributed to this report.