Look for suspicious activity. Counter-terrorism won't succeed without some participation form average citizens. This does not mean that you absolutely must confront suspected attackers, but you can do your part by keeping a watchful eye on your surroundings to detect behavior that may warrant further investigation. People who act nervously or unruly may pose a potential threat.
Notify the proper authorities if you detect evidence of a potential attack. Evidence could include notes found in bathrooms, encounters with suspicious people or unmonitored luggage. Someone who spends an exceptionally long period of time in the lavatory of the plane may also have a devious plan to mount an attack, but you should be absolutely certain the person poses a threat before you notify authorities.
Increase luggage security. Luggage is a place where would-be attackers can store instruments of crime. Increasing the number of random searches may foil plans for airplane attacks that X-ray scanners fail to expose. Tightening the standards for what items a passenger can carry can prevent would-be attackers from using items, such as glass bottles can also prevent airplane attacks.
Permit certain airline's personnel, such as flight attendants and pilots, to carry Tasers and handcuffs. Tasers provide non-lethal, but effective, force that can subdue even the most earnest would-be attackers. Tasers are advantageous because unlike a firearm they cannot pierce the cabin which can present danger such as loss of cabin pressure. They also render a person virtually immobile for a long enough period of time to then be able to restrain him with handcuffs.
