VIDEO: Boeing launches NASA astronauts for the first time after years of delays

Boeing launched astronauts for the first time Wednesday, belatedly joining SpaceX as a second taxi service for NASA. Watch video of the launch in the player above.A pair of NASA test pilots, Butch Wilmore and Suni Williams, blasted off aboard Boeing’s Starliner capsule for the International Space Station, the first to fly the new spacecraft. The trip was expected to take 25 hours, with an arrival Thursday. They will spend just over a week at the orbiting lab before climbing back into Starliner for a remote desert touchdown in the western U.S. on June 14.Here is everything you need to know about the historic Starliner mission:About the mission:In this mission, two NASA astronauts, Wilmore and Williams, will travel to the International Space Station in Boeing's Starliner spacecraft, which will sit atop United Launch Alliance's Atlas V rocket.Officials say it will take about a week for the astronauts to make it there.The purpose of the mission is to test the Starliner spacecraft and its subsystems, including maneuvering and docking, before NASA can certify the spacecraft for rotational missions.When and where was the launch?The Starliner mission was launched at 10:52 a.m. on Wednesday, June 5, from Cape Canaveral Space Force Station in Cape Canaveral, Florida. Who are the astronauts?The Boeing Crew Flight Test was the first time humans have traveled aboard Starliner, which has flown in the past without passengers. Wilmore and Williams, both NASA veteran astronauts, are on board.Wilmore is the commander of the mission and has been an astronaut for NASA since July 2000. He is a veteran of two spaceflights.Williams is the pilot of the mission and has been a NASA astronaut since 1998. She is a veteran of two space missions.Both astronauts went back home after the mission's many delays but returned to Central Florida last week for the scrubbed June 1 launch attempt. The two will spend eight days on the International Space Station if all goes as planned.Why was the mission delayed?When the original scrub was called on May 6, officials cited the cause as a mechanical issue involving "a liquid oxygen self-regulating solenoid relief valve on the Centaur upper stage" on the Atlas V rocket.Officials rolled the rocket back to its Vertical Integration Facility at Cape Canaveral Space Force Station and successfully replaced the pressure regulation valve, which prevents the oxygen tank from building up too much pressure.The launch was moved to May 17 to allow for more testing but was pushed back to May 21 when Boeing said Starliner teams were working to resolve a small helium leak detected in the spacecraft's service module.Then, the launch was pushed back to May 25 when officials announced they, once again, needed more time to resolve the issue.Eventually, officials said they would forego that May 25 launch attempt completely.The launch was indefinitely on hold until officials said they were prepared for a June 1 launch attempt.Last week, mission partners polled "go" to proceed with plans for that launch and rolled the Atlas V rocket out to the pad for the first time since the original scrub.On Saturday, the countdown was going smoothly, when suddenly, officials scrubbed the launch just minutes before takeoff. The sudden scrub was due to the failure of some ground support equipment.ULA said their teams worked overnight to identify the problem and were able to replace a faulty power supply system in their ground operations computers. The Associated Press contributed to this report