Delta Air Lines has signed an $8.5bn order with Boeing for 100 next-generation 737-900ER airplanes to replace its less efficient domestic aircraft.

The Boeing 737-900ER aircraft will replace Boeing 757 and 767 models and Airbus A320 aircraft in Delta’s fleet.

The US-based carrier has also ordered 200 fuel-efficient CFM56-7BE engines worth $2.2bn from CFM International, a joint venture between General Electric (GE) and Safran Group’s Snecma to power the aircraft.

The new, extended range aircraft will have technologically advanced wing design which will consume between 15% to 20% less fuel per seat and have lower maintenance costs.

The Boeing 737-900ER’s aerodynamic and structural design changes allow the aircraft to carry up to 180 passengers in a typical two-class layout.

Under the $8.5bn order, all of the airplanes will feature the new Boeing Sky Interior.

The aircraft are scheduled for delivery from the second half of 2013 until 2018.