Kelly Marie Tran and Naomie Ackie sent their congratulatory message shortly after Koch broke the record for the longest single spaceflight by a woman.
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"We hear that you (Christina Koch) are breaking the world record for the longest duration of space flight," said Ackie.
"By a woman. Yes, girl power!" Tran chimed in. "We're so inspired by your work."
Koch beat the record was 288 days set by former NASA astronaut Peggy Whitson by spending 289 days aboard the International Space Station.
NASA/International Space Station via Storyful contributed to this story.