I finished up my DFW Ambassador tour at approx 1400HRS and was just leaving the Ambassador's office when I heard what I originally thought was a prop aircraft taking off in runway 36C at DFW. In reality it was a single engine Cesna 182 RG on an East to West trip across DFW airport, passing about 100 ft or less ("in the grass" as explained by the ATC supervisor at the East Tower) over the Remote North building, AND crossing directly under a MD80 on takeoff from 36C. My initial thoughts were that this was a nut who had just committed a Class-B airspace intrusion (or is it incursion?). As he crossed 36C, he did a wing wobble which gave me the impression that he was experiencing some of the turbulence of the previous aircraft that had taken off. I'm already to crucify this guy for intruding on the airspace of that AAL MD80 that was taking off. I head home and call the supervisor of the East Tower, who tells me this gentleman I thought was a "nut", does this 2-3 times a week, "checking out the pipeline". He said when he crosses 36C, he then heads over the "tank farm". He said that all aircraft that are taking off are made aware of his presence, but to me this seems like a rather risky procedure in the first place, allowing an aircraft to fly at your 3 o'clock low position, while you are taking off. Is there anyone else on this list who MIGHT feel this way <grin>? Richard Whitenight DFW