The whistleblower lawsuit has had 16 delays since it was filed in 1999.
It is the 16th time justice officials have asked for a delay since the suit was filed in June 1999 by three current and former employees and a Washington-based environmental group.
Unlike the requests for the delay that expired Friday and another that expired on Jan. 31, Assistant U.S. Attorney Bill Campbell said attorneys for those who filed the suit agree to extend the deadline until April 2.
The suit claims that Lockheed filed false environmental reports that allowed it to collect hundreds of millions of dollars in operating bonuses. The suit claims the mishandling of radioactive material and other chemicals caused widespread contamination that is costing the federal government more than $1 billion to clean up.
The suits seeks to have the payments refunded. Those who filed the suit said they will continue to push it even if the government doesn't get involved.
Lockheed Martin has strongly denied the allegations, which are also being investigated by a federal grand jury in Louisville.