There are pretty much 2 crews/aircraft across the board. As the saying goes, "There are no holidays in the oil patch", so it's definitely a 365 days/year operation. Almost all jobs are 1 for 1, either 7/7 or 14/14, so you need 2 crews/aircraft. It's actually a little less than that, because there are a few 5/2 jobs, and not all aircraft are covered fulltime, but that's the norm. Most are single-pilot, but all mediums are 2-pilot, because FAR 135 requires 2 pilots for any aircraft configured with 10 or more passenger seats. Thus the number of pilots is more than twice the number of aircraft.