The VietJet Aviation Joint Stock Company has signed a $700 million contract to buy 15 engines from CFM International, a venture between General Electric and Snecma SA, a unit of France’s Safran SA. The engines will be installed on VietJet’s newly ordered Airbus A321 aircraft. The deal with CFM International is the second within a year, after a $300 million contract for engine maintenance signed in late November 2014.