Leaving aside Ruveyn's suggestion (that I can only assume was typed with tongue firmly planted in cheek...) I have two thoughts:
1) If a rational argument is going to help put this in perspective, then look at the numbers. The number of terrorism related aviation incidents in the USA can be counted on the fingers of two hands: 6 incidents involving commercial airliners (including the 4 on September 11, 2001), 1 involving a general aviation aircraft, and 3 incidents at airports. And that list covers a period of over 76 years, since the first sabotage of an aircraft in 1933.
The number of fatalities involved in all of these 10 incidents are a little over 3,000.
Let's take the worst year: 2001. In that year 622,131,000 people boarded 8,789,123 scheduled airline flights in the United States. 0.00045% of flights in that year were the subject of terrorist related activity. 246 passengers and crew were killed, or 0.00039%.
You have a better chance of being struck by lightning, or choking on your dinner than you do of being on board an aircraft in a terrorist event.
2) However, if, as I suspect, your fear is irrational, rather than rational, and that no amount of looking at the numbers is going to give you any assurance, in which case I suggest that you look for a counsellor to help you address your fear, and give you some strategies for working with it.
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--James