Boeing Commercial Airplanes landed an expanded contract for its 737 MAX jets from Icelandair, which increased its order from the 12 jets initially announced in December. The increase means the value of the projects is over $1.6 billion at Boeing’s current list prices.

The 737 MAX is a series of narrow-body jets that Boeing is developing to replace the 737 Next Generation. It will be the fourth generation of the 737 since the airliner was introduced almost 50 years ago. Three variants of the new series — 737 MAX 7, MAX 8, and MAX 9 — are due for a commercial debut in 2017.

The larger order from Icelandair includes 737 MAX 8s and 9s, along with purchase rights for eight more 737 MAXs. Boeing said the additional jets mean that the total number of 737 MAXs now on order is 1,180.

The 737 MAX will have larger, and more fuel-efficient engines than the current series. Boeing said the CFM International LEAP-1B engines would “deliver the highest efficiency, reliability and passenger comfort in the single-aisle market”.

Boeing v.p. for European Sales, Todd Nelp, predicted the new jets would help Icelandair to expand its operations across Europe and North America.

"The 737 MAX will complement our Boeing 757 operations seamlessly,” stated Bjorgolfur Johannsson, president and CEO of Icelandair, and allow us to continue our route expansion in the most fuel-efficient manner."

The Icelandair Group operates an all-Boeing fleet (passenger and cargo jets) with 23 Boeing 757 airplanes.