Boeing's Starliner spacecraft scored a crucial achievement last week with the delivery of two astronauts to the International Space Station, but problems encountered along its journey in space and more hurdles that lie ahead make the aerospace giant's goal toward routine missions a distant prospect.

In 2004—less than a year after the Columbia space shuttle broke apart upon re-entry into the Earth’s atmosphere, killing all seven crew members—President George W. Bush announced that the Space Shuttle program would conclude by the end of the decade.