“We are go for launch!” tweets NASA chief Jim Bridenstine. “@SpaceX and @NASA will continue monitoring liftoff and downrange weather as we step into the countdown. We are proceeding toward a 4:33 launch.”

Astronauts Bob Behnken and Doug Hurley will soon reach the launch pad, and the capsule hatch will close approximately two hours before the scheduled takeoff.

The mission could still be postponed, with the next launch window on Saturday.

Launch is scheduled for 4:33 p.m. EDT (2033 GMT).

No technical issues are being worked at this time, but weather remains a concern with a 40% probability of acceptable conditions for launch.

You can watch the SpaceX launch live here and on Space.com’s homepage, courtesy of NASA TV.

Space.com has been covering the lead-up to this epic mission extensively.

Update: Air Force One is flying near Launch Complex 39A where the Falcon 9 rocket and Crew Dragon spacecraft are being readied for launch.

President Trump should be landing momentarily to join the Vice President and other dignitaries to view this afternoon’s launch attempt.