Like any other kind of survival, knowledge is probably more important than gear. If you're concerned about the situation then learn a bit. Once you've learned something you can improvise something suitable to your techniques if you have the time. A Cross pen can either make nasty punctures or be a great pressure point device, depending on your base of knowledge. Of course, good enough and *RIGHT NOW* is usually better than a cool improv 60 seconds from now.

Weekend seminars can teach you a few tricks (a few *very useful* tricks) but getting those tricks slighly wrong can be worse than not knowing them in the first place. If you're really interested in prepartion you need repetition and practice such as can be found in martial arts schools and the like.

Remember when you're preparing that you're more likely to deal with a drunk than a terrorists so you want to know how to *not* kill someone.

Moving to specifics, if you want to control someone in an airplane asile you probably want to stay away from Aikido and Tae Kwon Do. Both of these arts can be cool but they're rather designed for more open areas. Jujitsu (traditional Japanese, not Brazilian) or similar joint locking/pressure point style would probably be best if you can find a good school. Karate would probably be a good middle ground.