NASA's much-anticipated launch of Boeing's Starliner spacecraft was abruptly halted just four minutes before liftoff on Saturday. This marks the second time the maiden flight for astronauts Sunita Williams and Butch Willmore has been delayed due to technical difficulties. The exact reason for the last-minute cancellation remains unclear as NASA has yet to provide details.

The launch initially faced scrutiny over an issue with the Atlas V rocket's topping, but this was resolved in time. Subsequently, the astronauts were secured in the spacecraft, and the latch was closed, signaling readiness for launch.

Sunita Williams, piloting the Starliner, and Willmore, serving as the mission's flight commander, are both veteran astronauts with previous experience on Shuttle missions. Their mission was to dock the Starliner with the International Space Station (ISS) after a 24-hour journey.

This mission represents the third space endeavor for Sunita Williams, who once held the record for the longest cumulative time spent in space by a woman, with a total of 322 days across two previous missions.

The United States is aiming to certify a second spacecraft capable of transporting humans to and from orbit, with SpaceX's Crew Dragon currently leading the commercial space race.

The Starliner, aptly named Calypso, boasts the ability to fly autonomously or be manually controlled and was expected to dock with the ISS following a 24-hour flight.

With the launch postponed, NASA is now likely to reschedule for one of the backup dates between June 2 and June 6.