Washington: Boeing's highly anticipated inaugural crewed test flight of the new Starliner space capsule faced a setback on Tuesday due to a technical glitch. The postponement, caused by an issue with a valve in the rocket's second stage, was disclosed during a live NASA webcast.

Indian-origin astronaut Sunita Williams was to fly into space for the third time as the pilot aboard Boeing's Starliner spacecraft. Boeing's Starliner was to blast off for the International Space Station from Cape Canaveral in Florida at 22:34 local time on Monday (8:04 am IST on Tuesday).

Starliner was to carry Williams, 58, and Butch Wilmore to the International Space Station. The mission has been delayed for several years because of setbacks in the spacecraft's development.

If it is successful, it will become the second private firm able to provide crew transport to and from the ISS, alongside Elon Musk's SpaceX. Such a scenario with both SpaceX's Crew Dragon and Starliner flying regularly is one for which the US space agency NASA has long waited.

Design and development is hard particularly with a human space vehicle, said Mark Nappi, vice president and Starliner programme manager at Boeing, during a Thursday news briefing.

There's a number of things that were surprises along the way that we had to overcome. It certainly made the team very, very strong. I'm very proud of how they've overcome every single issue that we've encountered and gotten us to this point, Nappi said.

This is Boeing's second flight to the International Space Station and third Starliner flight test overall, following a second Orbital Flight Test, the uncrewed mission also known as OFT-2, in May 2022. Boeing also completed pad abort demonstration in November 2019, according to NASA.

As the final flight test for Starliner, NASA's Boeing crew flight test will validate the transportation system, including the launch pad, rocket, spacecraft, in-orbit operational capabilities, and return to Earth with astronauts aboard, it said.

SpaceX and Boeing developed their respective vehicles under NASA's Commercial Crew Programme, a partnership with private industry contractors. From the outset, the space agency aimed to have both companies operating at once. The Crew Dragon and Starliner spacecraft would each serve as a backup to the other, giving astronauts the option to keep flying, even if technical issues or other setbacks grounded one spacecraft.

Williams received her commission as an Ensign in the United States Navy from the United States Naval Academy in May 1987.

Williams was selected as an astronaut by NASA in 1998 and is a veteran of two space missions, Expeditions 14/15 and 32/33. She served as a flight engineer on Expedition 32 and then commander of Expedition 33.

During her first spaceflight, Expedition 14/15, Williams was launched with the crew of STS-116 on December 9, 2006, docking with the International Space Station on December 11, 2006.

While onboard, she established a world record for females with four spacewalks totalling 29 hours and 17 minutes. Astronaut Peggy Whitson subsequently broke the record in 2008 with a total of five spacewalks.

On Expedition 32/33, Williams was launched from the Baikonur Cosmodrome in Kazakhstan, along with Russian Soyuz commander Yuri Malenchenko and Flight Engineer Akihiko Hoshide of the Japan Aerospace Exploration Agency, on July 14, 2012.

Williams spent four months conducting research and exploration aboard the orbiting laboratory. She landed in Kazakhstan on November 18, 2012, after spending 127 days in space.

During their Expedition, Williams and Hoshide performed three spacewalks to replace a component that relays power from the space station's solar arrays to its systems and repair an ammonia leak on a station radiator. With 50 hours and 40 minutes, Williams once again held the record for total cumulative spacewalk time by a female astronaut. The record has since been overtaken by Peggy Whitson. Williams has spent a cumulative total of 322 days in space.

Williams was born in Euclid, Ohio, to Indian-American neuroanatomist Deepak Pandya and Slovene-American Ursuline Bonnie (Zalokar) Pandya. She holds a physical science degree from the US Naval Academy and a Master of Science in Engineering Management from Florida Institute of Technology.