Once it does happen, the flight will kick off a series of events culminating in NASA astronauts Suni Williams and Butch Wilmore’s long-awaited trip back to Earth.

CAPE CANAVERAL, Fla. — A launch pad problem prompted SpaceX to delay a flight to the International Space Station on Wednesday to replace NASA's two stuck astronauts. The new crew needs to get to the International Space Station before Butch Wilmore and Suni Williams can head home after nine months in orbit.