At 56, astronaut Peggy Whitson is a lot younger than John Glenn was when he flew in a space shuttle at 77, but when Whitson launched Thursday with two other crew members toward the International Space Station she became the oldest female astronaut in the world to fly into space.
The launch was 3:20 p.m. EST Thursday, which was early Friday morning at the Baikonur cosmodrome in Kazakhstan.
Here's a look back at her barrier-breaking career.
Above: From left, France's Thomas Pesquet, Russia's Oleg Novitsky and NASA's Peggy Whitson wave to the crowd at the Russian-leased Baikonur cosmodrome before blasting off to the International Space Station.
This will be the third space station mission for Whitson. Her first was in 2002.
Above: Crew members head to the launch pad for the space shuttle Endeavour on June 5, 2002 at the Kennedy Space Center in Florida. Peggy Whitson is at center, second row.
Whitson became the first woman to command the International Space Station in 2007.
Above: Whitson smiles just before the launch of the Russian Soyuz rocket at the Baikonur cosmodrome on Oct. 10, 2007.
While Whitson was commanding the space station, the space shuttle Discovery, commanded by Pam Melroy, docked at the station, marking the first time both spacecraft had been commanded by women simultaneously.
Above: International Space Station commander Peggy Whitson poses with Pam Melroy, commander of STS-120, on Oct. 27, 2007 in the Unity node of the International Space Station.
Whitson has already racked up more time in space than any other female astronaut. Her cumulative total is a few hours shy of 377 days. Her upcoming six-month mission should push her beyond 534 days in space, the U.S. record set in September by 58-year-old astronaut Jeffrey Williams.
Above: Whitson participates in a spacewalk that lasted more than seven hours on Oct. 10, 2007. During the spacewalk, Whitson and astronaut Daniel Tani replaced a motor at the base of one of the station's solar wings.
The ground crew helps Whitson after her landing in northern Kazakhstan on April 19, 2008. The Russian space capsule landed about 260 miles off course in Kazakhstan but the three-member crew was safe.
Barbara Morgan held the previous record for world's oldest spacewoman. She was 55 when she flew a space shuttle mission in 2007.
Whitson will turn 57 while aboard the space station.
Above: Peggy Whitson smiles during an examination in Star City outside Moscow on Oct. 25, 2016.
The Soyuz MS-03 spacecraft that will carry Whitson and her two crewmates is transported to the launch pad at the Russian-leased Baikonur cosmodrome in Kazakhstan on Nov. 13, 2016.
Whitson gets her hair cut on Nov. 14 at the Cosmonaut Hotel in Baikonur, Kazakhstan. She will be the first woman to command two missions at the space station.
The Soyuz MS-03 spacecraft launches from the Baikonur cosmodrome with Expedition 50 crewmembers Peggy Whitson, Russian cosmonaut Oleg Novitskiy and France's Thomas Pesquet from the Baikonur cosmodrome early on Nov. 18.