CAPE CANAVERAL, Florida — Two astronauts who should have been back on Earth weeks ago said 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 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.