Early in that face-off, Commander Anderson asked repeatedly for permission to shoot. "I kept calling 'MIG-25' to the control agencies -- to the Awacs," he said. Such cautiousness was a strict requirement early in the air war, when the skies were filled with coalition aircraft. In order to avoid "blue-on-blue" encounters ("friendly fire"), the U.S. Rules of Engagement forbade a pilot's shooting at another plane without approval from the Awacs surveillance radar aircraft, whose crew could, theoretically, tell the good guys from the bad. And so, with that MIG right in front of him, Commander Anderson asked to be allowed to fire.
Permission was refused. "They didn't see him," he said. "My controlling Awacs did not see him."
Why? The Awacs can be foiled by a rare phenomenon called the "Doppler notch." When two aircraft are flying at or near the same speed and in the same general direction, both planes can vanish from the Awacs's radar screens.
Unless there was some human error, the MIG seems to have been obscured by this unusual glitch. And so, with no confirming blip before them, the Awacs personnel -- quite properly -- ordered the squadron leader not to fire.