We needed at least a 6 knt headwind to get out of Joburg the other night...then they switched runways so we had a tailwind, couldn't go, then it started raining, had to wait it out, ...then they switched runways back again...finally, 40 minutes later, we were 'leagal' to go, by 1k. We did fill up the airplane however, and I think there were about 23 non-revs. that got on.