I live in a rural farmland area, 15 miles from the nearest controlled airport. When I open B4UFly, there are half a dozen grass air strips within 5 miles. If I move out of range of those, there are that many more in that area. In 30 years, I've rarely seen any activity at any of them. I have no idea how to find contact information for any but a couple of them. Is there a central source of contact numbers? If I hear an airplane or helicopter, I immediately, visually locate it and decrease my altitude if necessary. I would also avoid flying in the vicinity of either end of the runways.