http://edition.cnn.com/2003/US/07/30...ing/index.html
From the story:

WASHINGTON (CNN) -- The Department of Homeland Security is warning that terrorists might be plotting suicide airliner hijackings this summer, with possible targets including sites in the United States and other countries.

"As of mid-June, Islamic extremists may have been planning suicide hijackings to be executed by the end of summer 2003," according to a document CNN obtained Tuesday.
[snip]

Does this affect your travel plans? As for me, no, but I really can't face the prospect of how terrible another 9/11 would be.