Watch: WWII Vintage P-51 Mustangs flyover Seattle

The unique formation honored the 70th anniversary of D-Day, one of the most important days in U.S. history.

The lead Mustang in the formation flew four sorties on June 6, 1944 over the beaches of Normandy.

Nicknamed "their little friend" by Allied bomber crews in World War II, the P-51 Mustang emerged in 1942 as the fast, high-altitude fighter that could escort bombers deep into enemy territory and turn the tide of losses sustained during long-range missions.