It was a Saturday in June, in the middle of the afternoon, a clear day, in open country-a most perilous time and place. Three sport airplanes-a Pitts S-1, an Acro Sport and an RV-6-were on their way from an airshow at the Longmont Airport, on the north side of Denver, to Centennial Airport at Englewood, on the south side. Longmont and Centennial are only 30 nm apart as the crow flies, but the crow doesn't know about Class B airspace. Denver International lies between the two airports, and so to get from one to the other requires a knight's move to the west around the Denver TCA. Several complications dot this route; the first is the Boulder Airport, an uncontrolled field with considerable soaring activity, located about eight nautical miles south of Longmont.