The space agency expects the program’s maiden mission to take place sometime in 2020.
Boeing and SpaceX were awarded contracts worth up to $6.8 billion combined in September 2014 to ferry astronauts to and from the space station with the CST-100 and Dragon spacecraft.
Each contractor received four additional ISS transport missions in January of last year.
The Aug. 3 mission will also mark Americans’ first trip to space from U.S. ground since the Space Shuttle program concluded seven years ago.