Upgrades included new navigational avionics that allow faster and more secure integration of the aircraft into general air traffic and a reconfigured interior to allow the tankers to carry conventional cargo pallets.
The upgrades on the three aircraft are being conducted under a $44.5 million award given to Rockwell Collins last year through the U.S. Foreign Military Sales program.
The French Air Force said the upgraded aircraft will perform a series of test and evaluation flights later this year to establish specific operating and maintenance procedures.
The first of three planes was delivered to Air Base 125 at Istres, located in southern France, late last week by an American flight crew.
Information on a schedule of delivery for the remaining aerial tankers was not provided by the air force.