HANOI, Oct 31 (Reuters) - Vietnam"s VietJet Aviation (VJC.HM) on Sunday signed a $400-million contract with Rolls-Royce for the provision of aircraft engines and services, the budget airline said. The deal for the Trent-700 engines for widebody aircraft was signed in Edinburgh at the presence of Vietnam’s Prime Minister Pham Minh Chinh, who is heading to Glasgow to attend the United Nations COP26 summit, the airline said in a statement.