On June 16, 2005, about 1445 central daylight time, a Cessna 150M, N45372, registered to and operated by Boomer Aviation, Inc., collided with the ground and nosed over on final approach at Panama City - Bay County International Airport, Panama City, Florida. The aerial advertising flight was operated under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual meteorological conditions prevailed. The commercial pilot received minor injuries, and the airplane sustained substantial damage. The local flight departed Panama City - Bay County International Airport about 1400. The pilot stated his first flight in the airplane that day began about 1000, and he had a total of six banners to fly. He stated he flew the first three banners, landed to fuel the airplane, then departed to finish the final three banner tows. The pilot stated he returned to the airport and dropped his last banner, and "because of [the banner tow operation's base location] ... on the airport, I was already on a left downwind for runway 05." The pilot was cleared to land on runway 5, and he stated the airplane was stable on base at "60 on the [airspeed]" and 20 degrees of flaps. The pilot stated that, while on final approach, "I noticed a large downdraft. I responded with full power and initiated a go-around." The pilot stated the airplane continued to descend, and it collided with the ground approximately 100 feet short of the runway 05 threshold and nosed over. Examination of the accident site revealed the airplane was inverted. The nose landing gear strut was displaced aft, the nosewheel was separated, the underside and the front of the engine cowl were crushed, the propeller was separated, the windscreen was fragmented, the top of the vertical stabilizer and rudder were crushed, both wings were damaged, and the right wing was partially separated at the wing root. The pilot reported no mechanical malfunction with the airplane, and he stated the accident was a result of an "undetectable, unnoticeable micrometeorology event [and] windshear in combination with a large thermal downdraft." A review of recorded weather data from the airport's automated surface observing system revealed at 1453 conditions were winds from 260 degrees at 10 knots, visibility 10 statute miles, skies clear, temperature 33 degrees centigrade, dew point 22 degrees centigrade, altimeter setting 29.80 inches Hg. Meteorological review of upper wind data, Doppler Weather Radar images from Eglin Air Force Base, Florida, and GOES-12 satellite images showed no significant weather.