Boeing ( BA) got a $9.7 billion contract from the Air Force Thursday to build 60 more C-17 Globemaster III transport aircrafts, bringing the Air Force's total fleet of C-17s to 180.

The C-17, which most recently flew equipment, troops and supplies into Afghanistan, is built by Boeing's Integrated Defense Systems (IDS) in St. Louis. Since 1991 Boeing has manufactured 89 of the heavy-duty aircraft for the Air Force.

The C-17 "is uniquely adapted to the challenges faced by today's transforming military, which needs to mobilize forces quickly and effectively -- whether against military adversaries or natural disasters," said George Muellner, vice president and general manager of Air Force Systems at Boeing.

Boeing did not say when it expects the planes to be completed.