The first astronauts to fly Boeing's troubled Starliner are definitely not "stranded" at the International Space Station, NASA insisted Friday despite having no clear timeframe for bringing them home.

In an unusually defensive press call, officials attempted to put a positive spin on where things currently stood after weeks of negative headlines due to the spaceship's delayed return.

Astronauts Butch Wilmore and Suni Williams blasted off on June 5 following years of delays and safety scares affecting Starliner, as well as two aborted launch attempts that came as astronauts were strapped in and ready to go.

They docked the following day for what was meant to be roughly a week-long stay, but their return has been pushed back multiple times because of thruster malfunctions and helium leaks that came to light during the journey.

"Butch and Suni are not stranded in space," declared Steve Stich, NASA's commercial crew program manager.

He added the pair were "enjoying their time on the space station" and "our plan is to continue to return them on Starliner and return them home at the right time."

Before that can happen, however, ground teams need to run more testing to better understand the root causes.

It was known there was one helium leak affecting Starliner before the launch, but more leaks emerged during the flight. While non-combustible, helium provides pressure to the propulsion system.

Separately, some of Starliner's thrusters that provide fine maneuvering initially failed to kick in, delaying docking. Engineers are not sure why Starliner's computer "deselected" these thrusters, though they were able to restart all but one of them.

The thruster testing could begin July 2 and would last at least two weeks, said Stich.

"It is pretty painful to read the things that are out there," added Mark Nappi, Boeing's vice president and program manager of its Commercial Crew Program.

"We've gotten a really good test flight that's been accomplished so far, and it's being viewed rather negatively."

Teething issues with new spaceships aren't uncommon, with the Space Shuttle program facing its share of problems in its early days.

But the Starliner program has suffered from comparisons to SpaceX's Crew Dragon. Both companies were awarded multibillion dollar contracts in 2014 to provide the US space agency with rides to the ISS, with SpaceX succeeding in 2020 and carrying dozens of people since.

Aerospace giant Boeing's reputation has also nosedived in the wake of the safety scandal surrounding its 737 Max passenger jets.