United Continental said it will buy 100 Boeing 737 MAX 9 aircraft and fifty 737-900ER planes in a deal that Boeing valued at USD$14.7 billion at list prices.
United Continental, the holding company that owns United Airlines, the world's largest carrier, said it will begin taking delivery of the 737 MAX 9s in 2018.
Airlines usually get discounts and United did not disclose what it agreed to pay Boeing for the planes.
The 100 737 MAX aircraft order will allow United to replace older, less-efficient aircraft to reduce fuel and operating costs, the company said in a statement.
Boeing said the combined order will allow it to exceed 10,000 orders overall for the 737 family. The 737 MAX is a new-engine variant of Boeing's Next-Generation 737.
The additional order for fifty 737s, which will be delivered from late 2013, reflects efforts by both Airbus and Boeing to maintain production of their current products and ensure a smooth transition to newer models.
United Continental said the 737-900ER models will replace older, less-efficient Boeing 757-200 aircraft flown domestically.
The new models are expected to burn up to 15 percent less fuel per seat than the aircraft they replace, the company said.
The new set of orders takes United's order book to 272, including 50 Boeing 787 Dreamliners, the airline said.
United Continental will be the first North American carrier to fly the much-awaited light-weight, carbon-composite wide-body 787.