My guess is they are hiring and firing pilots as an almost weekly affair. Most corporations with 6-8 jets can staff the flight department without having to advertise externally at all. Corporate flight departments tend to be known in the pilot community, and a name itself is usually more than enough to draw resumes. The only time you see an ad is when they are trying to comply with unfair hiring practices and an ad will pop up and disappear in the internal job board. Going public and staying there like this is pretty unusual.