Sunita Williams and Butch Wilmore in the International Space Station (ISS)
The death of Indian-origin American astronaut Kalpana Chawla and six others on February 1, 2003 when the space shuttle Columbia broke up and burnt as it re-entered the Earth's atmosphere played heavily in the minds of NASA officials, who decided to keep another Indian-origin American astronaut, Sunita Williams, in space for eight months.
Before the Columbia accident, the space shuttle Challenger had exploded and killed all crew on January 28, 1986. In all, 14 astronauts have lost their lives in these accidents.
The two accidents "very much affected the decision" to bring Boeing Starliner back without the astronauts, said NASA chief Bill Nelson, who is himself an astronaut and has been part of the investigations into the two space shuttle accidents. He said "obvious mistakes were made" by the National Aeronautics and Space Administration (NASA).
Kalpana Chawla died over the skies in southern US when the space shuttle Columbia and her crew broke apart during re-entry, 16 minutes prior to the scheduled landing. She went to Tagore School in Haryana's Karnal in 1976, and graduated with a BSc degree in aeronautical engineering from Punjab Engineering College in 1982. She joined NASA as an astronaut in 1994, after completing further education in the US.
Mr Nelson said the culture in NASA back then was such that despite junior flight engineers warning of risks, none heard them. "Today, folks are encouraged to speak their minds," he added.
So, NASA took the decision to bring home astronauts Sunita Williams and Butch Wilmore in February 2025, instead of now, in the SpaceX Crew Dragon after engineers spoke their mind about the risks involved in flying the spacecraft in its current condition.
NASA officials said the decision to replace the return spacecraft was "unanimous".
"Spaceflight is risky, even at its safest and most routine. A test flight, by nature, is neither safe nor routine. The decision to keep Butch and Suni aboard the International Space Station (ISS) and bring Boeing's Starliner home without crewed is the result of our commitment to safety - our core value and our North Star," said Mr Nelson.
Space engineers identified helium leaks and experienced issues with the spacecraft reaction control thrusters or small rockets on June 6, as Starliner approached the ISS.
NASA in a statement had said the "uncertainty and lack of expert concurrence does not meet the agency's safety and performance requirements for human spaceflight."
NASA then announced it would bring home Boeing's Starliner without the two astronauts by September 6. It will take six hours to return the Starliner to Earth. The spacecraft has had two uncrewed missions before this one, and Boeing is hopeful that it will return safely.