For personnel and wages don't mess with anything go to settings and tick the automatic wages and personnel boxes.
Saying that however, the only time you do want to mess with the personnel dept is if you have a base you close down, then you have to sack staff because you'll have too many staff and I've found that the airline doesn't sack the staff for you and you'll have a massive wage bill.
On the staff page you'll see how many you need and how many you got, just bring the number of staff down to what is needed, yes your company image will lower in points, but it rebuild over time and don't forget, after the sackings, put your hire and fire staff back to automatic.
Hope this helps
PS I'm sure someone else will stick some more advice on here for you as well