Lockheed's most capable engineer, Clarence "Kelly" Johnson, and a team of designers began work on a prototype, designated the XP-80 but nicknamed "Lulu-Belle," on June 21, 1943. Lulu-Belle" flew on January 8, 1944, and later starred in a series of exercises conducted to develop tactics that American heavy bomber crews could use against attacks by jet fighters. The trials showed that enemy jet fighter pilots would much prefer rear aspect attacks. Based on these findings, AAF planners moved the formations of American fighters protecting the bombers to higher altitudes. Highlighted in this image are the vertical stabilizer and horizontal stabilizer of the Lockheed XP-80.