NASA and Boeing are grappling with how best to bring two U.S. astronauts back to Earth.

Originally planned to last just eight days, leaks and other technical issues suffered by Boeing's

Starliner spacecraft on its way to the International Space

Station have delayed the planned return flight by more than two months, and that has left its

two astronauts, Butch Wilmore and Sunny Williams stuck in space.

To help us understand what it all means, we're joined now by our science and aviation

correspondent, Miles O'Brien, Miles, it's always great to see you.

So what went wrong with the starliner?

Well, there were signs of trouble from the get-go, Jeff. There were helium leaks on the launch pad.

NASA and Boeing huddled. It would have required a significant delay,

a rollback to the hangar to do the work to try to fix those leaks. Helium is a very difficult thing to track down,

but they still decided to launch.

In retrospect, maybe that wasn't a great idea

because once they got in orbit,

the helium leaks persisted.

And then as they approached the docking phase at the

International Space Station seven thrusters which guide it the capsule through

the void of space failed inexplicably and so at the bottom of the ledger here

the engineers are scratching their head still they don't know if the helium leak is

linked to the failed thrusters.

They don't know the root cause.

They've been testing hardware on the ground,

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