Ideally you would like to do airborne surveys in areas free of traces of civilization because as Donypee mentioned they can interfer with the readings. That said, many surveys are conducted in areas that have power lines, machinery, mines etc. The crew makes note of these man made anomalies or they are recorded on photos (that are taken as the airborne survey is conducted). As the results are compiled the notes and photos are reviewed.
I suspect the bigger reason for the delay is that the airborne survey drives the ground follow-up surveys which define the drill targets. Each has to wait for the other to be finished and analyzed so that the next can be done right. In the McFauld Lake projects they are compressing what should be a year long cycle into a couple of months. Most of these guys are flying by the seats of their pants as they try to keep up with the pace of events in the area. Add to that, the comments from several people that NOT's camp is full to capacity and that there is a shortage of drills.
The one not mentioned is that NOT is the operator on most of these JV's and I bet NOT is stretched to the limit with its core project. Shaking loose drills and people to work the JV projects when they have investors clamouring for NRs is going to be tough.
We have to remember that the field crews will be at this non-stop for a couple of years and burn out is the norm. They are probably just getting to the stage where they realize that the way they have done things in the past is not going to survive the demands of the project. Hopefully they have been ramping up their equipment and staff including hiring some good senior field geologists to manage the JV projects and take some of the pressure off.
Just my thoughts.
.... Been There