The 777-300ER deal was valued at $3.3 billion "at average list prices," and includes an option for 10 more of the aircraft, which carry up to 365 passengers, according to a statement from the two companies.
A value was not given for the 787 purchase.
"Our decision to order the 777-300ER is part of a long-term growth strategy to expand and modernise our fleet with newer, more fuel-efficient airplanes,' Saudi Airlines director general Khaled al-Mulhim said in the statement.
"We see direct benefit because of the 777-300ER's improved fuel efficiency, seat-mile costs and the economics of operating a twin-engine airplane over long distances."
Mulhim said that most of the aircraft were to be used as part of a programme to rationalise domestic services and increase seating capacity by 20 per cent, according to the official SPA news agency.
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