A federal grand jury in Baltimore indicted Martin Thomas Bradley, an Andrews Air Force Base mechanic, Tuesday, charging that he caused a bomb to be placed in his wife's suitcase before she took a Braniff flight from Washington's National Airport on March 2.

Bradley, 27, was arrested by FBI agents March 3 after his wife, Staff Sgt. Mary Jo Bradley, found a plastic explosive device in her luggage when she arrived at a Wichita Falls, Tex., Air Force base for a three-month training course. Federal Aviation Administration officials are investigating how the bomb passed undetected through National Airport's security measures for checked luggage.

"It's not that frequently that we find a bomb that goes all the way through," said assistant U.S. attorney Michael Schatzow.

Fred Bennet, a federal public defender representing Bradley, said Bradley will enter a plea of not guilty when he is arraigned in a Baltimore district court. No date has been set for the arraignment.

"My client believes he is not guilty and would like a jury trial," Bennet said.

Bradley is being held in the county detention center in Upper Marlboro on $400,000 bond.

Charges in the three-count indictment against Bradley carry jail terms of up to 30 years and fines of up to $20,000, authorities said.