The military officials said the Iranian planes had no hope of escaping American detection.
"The Iranian plane was flying over its territory and over international waters."
The Iranian planes were fired on as they approached an American surveillance plane.
The officials said they believed the Iranian plane left without its cargo, but they were not sure.
An Iranian plane picked up 35 pilgrims injured in the riots and the bodies of 58.
The American ship's crew shot down the Iranian plane in the mistaken belief that the aircraft was a military fighter.
Captain Rogers waited until the Iranian plane was within nine miles of his ship, then ordered missiles fired.
The Vincennes initially reported the altitude of the Iranian plane as 7,500 feet and descending.
The Pentagon added that the Iranian plane was shot down "during these defensive maneuvers."
Without such directions from the controllers, they added, a crew would be obliged to stay within the corridor, as the Iranian plane apparently did.