In July 1956 the Greek State reached an agreement with Greek shipping magnate Aristotle Onassis for Onassis to purchase the airline. The company flew under the T.A.E. name until the end of the year and for the first few months of 1957. On 6 April 1957 the company was renamed Olympic Airways (Ολυμπιακή Αεροπορία/Olympiaki Aeroporia).
The new company developed rapidly. To allay the distrust of air transport by Greeks, Onassis developed the “aviation days of ’57” scheme, providing short, free flights in a DC-3 to demonstrate the reliability of air travel. Onassis always wanted to be in the cutting edge of the technology, so in 1959 he signed a deal to buy four de Havilland Comet 4B that in 1960 was Olympic’s first jet aircraft, that entered service. Olympic and British European Airways created the first codeshare flights; later the companies expanded their cooperation. When Greek crews had to spend a night in London, British crews would fly the Olympic Comets to BEA destinations, and the same with Greek crews and BEA Comets. On all BEA and OA Comets, there would be a “BEA-OLYMPIC” sign. In 1962 Olympic set a record flying a DH Comet 4B from London to Athens in just two hours and 51 minutes.