Understanding where harmful gases like ozone originate is key to making improvements. The physics is simple, gases are transported from regions upwind, from higher altitudes by entrainment, to or from the surface or locally produced. The airplane makes the perfect 3 dimensional research tool, it can fly upwind to measure horizontal transport, it can fly spirals above your city to measure vertical transport. With some judicious assumption about deposition to the earth’s surface, and knowledge of the temporal change, we can solve for the local production. In so doing, ozone increases can be apportioned to their respective sources, and mitigation budgets can be maximized!