I think calling in airport bomb threats that morning, presuming that time hadn't been altered before then, makes the most sense. It would tie in with the existing intel about imminent attacks.
If I had to play the long game, what I would do is start correspondence with a journalist. Make it clear I know about the future and make some very basic predictions about events in late 1996 into 1997 that evidently come true. Keep doing that for years if need be. Whatever authority cares will find me.
If you keep hitting the ball out of the park like that, all kinds of people would be all over you long before 9-11, e.g., financial outfits would be offering you billions. Cultists would want to make you their leader.
A more realistic approach is to simply point out how vulnerable cockpits are to attack, and try to get the New York Times or 60 minutes or Frontline or someone to take an interest, and even threaten to stage an attack if something is not done to secure them.
True story. Back in the day my Dad flew first class rather frequently on business, often from LA to London. Several times he was invited into the cockpit to fly the plane, and he did. That was a first class amenity, particularly for international flights. One time the plane had to make an emergency landing at Ft. Churchill in the dead of winter, and he spent three days there in quonset huts. Every morning after defrosting the tires, the passengers would hike a quarter mile to the plane, and it would try to take off and fail and would skid down the runway to a stop. Rinse and repeat until finally they flew another plane in 3 days later. The temperature was 40 degrees below zero and windy, and he wearing only a top coat. That was when my Dad learned that teeth chattering cold was not merely a turn of phrase. And no my Dad was not flying the plane during these take off attempts, in case you were wondering.
