This logo was used, in variations, until 1962. The wing on the left is left over from their first logo, and represents the Roman of travel and commerce, Mercury.
In 1953, Delta merged with Chicago & Southern Air Lines which changed Delta's name to Delta C&S. Delta would keep that name for the next two years.
Delta Air Lines (Second era)
Using the triangle "widget" (representing the greek letter Δ "Delta")from their first jet service (Delta Royal Jet Service) logo turned sideways, Delta used this logo to symbolize the speed of jets.
The logo was created for America's bicentennial celebrations.
In early 2000, Delta were persuaded by Landor Associates to make a number of changes to their identity. This included dropping "Air Lines" from their logo and softening the arch in the triangle.
In July 2004, Delta reverted back to the sharper widget symbol, partly due to employee suggestions and to coincide with the company's 75th anniversary on June 17, 2004. There were, however, no other changes to the livery.
On April 30, 2007, Delta Air Lines presented a completely new look, the same day the airline emerged from bankruptcy. The triangle is now all red, with one side in a slightly darker shade to give the symbol some depth. Lippincott Mercer created the new identity.