BUFFALO, N.Y. (AP) — A freight contractor for the military admitted overbilling the Defense Department by millions of dollars and agreed to pay $28 million in fines and restitution.

National Air Cargo's guilty plea to a corporate felony charge in U.S. District Court settles an investigation begun by a whistleblower's call nearly two years ago. Military and FBI investigators found that the company overbilled the government $4.4 million from 1999 to 2005 by charging air rates for ground deliveries and claiming deliveries were made sooner than they actually were.

U.S. Attorney Terrance Flynn said the investigation focused on military bases within the U.S., and there was no proof anything was done that affected national security or the war effort.