Boeing Commercial Airplanes has settled terms with Delta Air after the carrier cancelled an order for 18 Boeing 787-9 Dreamliner jets, a contract worth $4 billion at current list prices.

Delta had inherited the purchase commitment from Northwest Airlines, the rival carrier it acquired in a $2.6-billion share-exchange in 2008.  Subsequently, in 2010, Delta negotiated a deferred delivery on the planes until after 2020.

The specific terms of the Delta-Boeing settlement were not announced, but the airline noted it would take delivery of 120 new 737-900ER aircraft, through 2019.

“This business decision is consistent with Delta’s fleet strategy to prudently address our widebody aircraft needs,” according to a statement by Delta senior vice president Greg May.

While Delta also deferred delivery for four Airbus A350s earlier this year, from 2018 to 2019-2020, it still has orders for 25 of those widebody jets, as well as 25 A330neo jets.

The 787 Dreamliner is a twin-engine, long-distance aircraft seating 242 to 335 passengers (depending on the variant), developed at a time when airlines were eager to reduce fuel consumption and maximize traffic opportunities with numerous point-to-point routes. More recently, those strategies have reemphasized narrow-body jets, like the 737 series, which may be more efficient for short and mid-range routes.

“Delta is one of the world's largest operators of Boeing aircraft and our valued partnership with Boeing will remain strong as we safely and comfortably serve our customers across the world every day,” May stated. This business decision is consistent with Delta's fleet strategy to prudently address our widebody aircraft needs.”