I agree, I wouldn't be comfortable approaching an airport checkpoint with a 4 inch folding knife. It would seem like an obvious potential weapon. I checked it again at the link below and it said:<br><br>"Knives with a blade length in excess of four inches (10.2 cm) are not allowed on board aircraft in the U.S. State or local laws in the U.S. may restrict the carraige of smaller knives. Other prohibited weapons include throwing stars, swords..."<br><br>http://www.airsafe.com/danger.htm<br><br>Of course, the way this is worded, it doesn't specifically allow knives of less than 4". <br><br>