The iconic line has become so familiar that it might be hard to imagine it any other way: as the first man on the moon put it during the space program, his achievement was “one small step for man.”

But what if the first human being on the lunar surface had been a woman ?

That’s a central question asked by the Netflix documentary Mercury 13 movie, directed by David Sington and Heather Walsh. The Mercury 13 women in question were a group of experienced hidden figures female pilots — Jerrie Cobb, Janey Hart, Jan Dietrich, Marion Dietrich, Rhea Hurrle, Irene Leverton, Bernice Steadman, Jean Hixson, Gene Nora Stumbough, Jerri Sloan, Myrtle Cagle, eileen collins, Sarah Lee Gorelick and Mary Wallace Funk — who in the early 1960s were invited by Dr. Randolph Lovelace, who had also been involved in testing male pilots for the same reason, to take the tests he had given to the Project Mercury astronauts. Cobb was the first woman to undergo the testing and training program , and after she passed the test the other women were invited to participate.

The women featured in the Mercury 13 movie passed through some of the same physiological and psychological testing procedures as Nasa’s first male astronauts, as the space race with Russia ramped up in the early 1960s. In some cases, the women, each of them skilled flyers, fared better than their male counterparts, but their testing, which was designed to assess their suitability for space flight, was conducted with private funding without the approval of Nasa.

Mercury 13 is a remarkable story of the women who were tested for spaceflight in 1961 before their dreams were dashed in being the first to make the trip beyond Earth. NASA's 'man in space' program, dubbed 'Project Mercury' began in 1958. The men chosen - all military test pilots - became known as The Mercury 7. But away from the glare of the media, behind firmly closed doors, female pilots were also screened. Thirteen of them passed and, in some cases, performed better than the men. They were called the Mercury 13 and had the 'right stuff' but were, unfortunately, the wrong gender. Underneath the obsession of the space race that gripped America, the women were aviation pioneers who emerged thirsty for a new frontier, but whose time would have to wait. The film tells the definitive story of thirteen truly remarkable women who reached for the stars but were ahead of their time. A Netflix original documentary directed by David Sington (The Fear of 13) and Heather Walsh.

These women were tested for “the right stuff” by NASA doctor William Lovelace almost 60 years ago and proved themselves to be just as good as, if not better than, the Mercury 7 astronauts in withstanding extreme physical and psychological tests. Results of the tests eventually lead to the inclusion of women within NASA’s astronaut corps, with Sally Ride paving the way for American women in 1983 and Eileen Collins becoming the first female pilot to command a space shuttle in 1995.