There are a number of factors to bear in mind here when you look at any potential effect on the airline industry.
1) Oil prices - already oil prices have surged ahead in the expectation of a conflict in Iraq, up to levels approaching US$30/bbl. This is very bad news for the airlines as it imposes yet another cost burden on already financially weakened operators, which will mean higher ticket prices ... and which in turn will result in fewer passengers travelling.
2) Fallout from 9/11 - don't forget that anything approximating 9/11 didn't happen prior to the Gulf War. Now, airlines are already in a very shaky state and Americans in particular are very scared to travel overseas.
The added threat of Al Qa'aida terrorism will have the effect of grounding many of the few remaining passengers.
I do not expect this to have much effect on regional airlines operating in areas outside the US and the Middle East. Long haul operations to destinations outside the US should also not be seriously affected.
However, I am gravely concerned about the future for the majority of US airlines. I suspect that a new Gulf conflict - especially one without any legitimate basis by the US - will result in Chapter 7 for major airlines such as American, United and USAirways.
On the other hand, the future is bright for cargo operators!