The 11 count indictment was returned Wednesday in Fort Worth on the four defendants.
Each is indicted on several counts.
They are identified as 53 year old John Gilmore, III of Wichita Falls.
He's a former lead civil engineer in the 82nd Civil Engineering Squadron at Sheppard; 60 year old Larry Ballard, also from Wichita Falls, who is an engineer under the supervision of Gilmore; 50 year old James Freeman of Vernon, seen here from an arrest in 1994 in Wichita County.
He owns Freeman Construction, a road building and paving company; and 63 year old Miguel Hughes of Fort Worth, the owner of Hughes and Guzman Construction.
Sheppard officials say Gilmore and Ballard worked with Defense Support Services, a federal contractor at Sheppard, but they say the company has since suspended the men.
The four defendants are charged with conspiring to leak sensitive information to friends so they could be awarded government contracts.
Freeman and Hughes are accused of paying thousands in cash bribes, travel expenses, travel expenses and other gifts to Gilmore and Ballard.
The indictment states the activity started around the mid-1990's and continued until about late April 2009..
Sheppard officials condemned the men's alleged actions and they have fully cooperated with the Department of Justice since the investigation started.
"We expect our employees to uphold the highest ethical standards and obey the law and a vast majority do just that. However, we are committed to holding them accountable when they don't do that," says George Woodward, director of public of affairs at Sheppard Air Force Base.
Each count of the indictment carries a maximum sentence of five years in prison and a $250,000 fine.
Gilmore, Ballard and Freeman will make their initial appearance in federal court in Wichita Falls Friday at 10 a.m., while Friday at 2 p.m. is when Hughes will appear in federal court in Dallas.