So being a few times at my daughter's north of Lake Minnetonka I've noticed a loose train of these A/C coming in from , it seems, the NW as this quite a ways out and landing tonight about 2000hrs on one of the parallels. I walked out to see the first of three-how many before I don't know. I think I noticed 4-5 another night. Seems kinda strange. The Nodak oil folks? Anybody know?