Depends on where the craft is. If it is in low earth orbit, then the air will start out in orbit, similar orbit to the craft it leaked from, and the molecules will soon thereafter interact with other air molecules, slowing down and being pulled back into earth’s atmosphere.
In deeper space, it will just spread out and be caught up in the solar wind and pushed into the outer solar system, or even out into interstellar space and make up part of the low density interstellar medium.
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