He didn't buzz the car.
If my memory is correct, he was on a legit flight path, but the map that was used didn't have the gondola (and cable) marked on the map.
Over the course of the trial, it was found that the plane was flying at speeds in excess of 500 miles per hour--faster than military regulations allow--when it hit the cable car wire.
The cable car wire hung at 260 feet, over 700 feet below the military-approved altitude of 1,000 feet.
Additionally, it came out in the trial that the military-issued map that the pilots were using did not show the cable car.