Clan Douglas
Douglas initially used a logo that combined two letter Ds and wings, and two Ds joined as a heart as a reference to the Clan Douglas. After the success of the DWC, the company adopted a logo that showed three airplanes circling a globe. The logo eventually evolved into an aircraft, a missile, and a globe. This logo was later adopted by McDonnell Douglas in 1967, and became the basis of Boeing's current logo after their merger in 1997.