More U.S. military aircraft are to receive protection against shoulder-fired missiles through a contract modification issued by the U.S. Air Force.

Under the modification to an earlier fixed-price award, Northrop Grumman will produce hardware and support for the Large Aircraft Infrared Countermeasure system, or LAIRCM.

LAIRCM, which is a lightweight and compact system, detects a launch of a man-portable, infrared seeker missile and activates a high-intensity laser-based counter-measure system to track and defeat the missile.

In 2012, the Air Force gave Northrop a $334 million contract to supply the system -- in use by the Air Force since 2001 -- through April of this year for use on C-5 Galaxy, C-17 Globemaster III and C-130 Hercules aircraft.

Northrop Grumman said that under the $238 million contract modification, it will supply additional system transmitters, missile warning sensors, processors, lasers, control interface units and supporting equipment.

The equipment will be supplied through April 2016.