Two astronauts who should have been back on Earth weeks ago said on Wednesday that they're confident that Boeing's space capsule can return them safely despite a string of vexing breakdowns.

NASA test pilots Butch Wilmore and Suni Williams were launched aboard Boeing's new Starliner capsule early last month, the first people to ride it. Helium leaks and thruster failures almost derailed their arrival at the International Space Station and have kept them there much longer than planned. Now the earliest they could return may be the end of July, officials said.

In their first news conference from orbit, the pair said they expect to return once thruster testing is complete here on Earth. They said they're not complaining about getting extra time in orbit and are enjoying helping the station crew. Both have previously spent stints at the orbiting lab, which is also home to seven others.

"I have a real good feeling in my heart that the spacecraft will bring us home, no problem," Williams told reporters.

The test flight should have lasted eight days, ending on June 14.

NASA's commercial crew program director Steve Stich said the earliest the Starliner astronauts might return is the end of July. The goal is to get them back before SpaceX delivers a fresh crew in mid-August. But that, too, could change, he noted.

This week, NASA and Boeing are trying to duplicate the Starliner's thruster problems on a brand new unit at White Sands Missile Range in New Mexico, one of the prime landing sites in the U.S. western desert. The trouble is in the propulsion system used to maneuver the spacecraft.

Five thrusters failed as the capsule approached the space station on June 6, a day after liftoff. Four have since been reactivated. Wilmore said there should be enough working thrusters to get him and Williams out of orbit. There are also bigger engines that could fill in if necessary.

Boeing's Mark Nappi stressed that in an emergency, Starliner and its crew could return right now. While the company does not believe the thrusters are damaged, "we want to fill in the blanks and run this test to assure ourselves of that," he said.

NASA ordered the Starliner and SpaceX Dragon capsules a decade ago for astronaut flights to and from the space station, paying each company billions of dollars. SpaceX's first taxi flight with astronauts was in 2020. Boeing's first crew flight was repeatedly delayed because of software and other issues.

There have been no discussions with SpaceX about sending a rescue capsule, Stich said.