Assuming the flights to those cities are even running (as of this weekend, there were still horrible delays for most airports), I think you should go. I guess my attitude is that the terrorist threat has always been there, whether we chose to acknowledge it or not, and flying right now is probably the safest it's been in years, because security is so heightened -- between the plain-clothes Delta forces and the Air Marshals, I actually think I will feel more secure in some ways.
Unless you are planning to only interview at schools within driving distance from this point forward, you will have to get on an airplane at some point this year. I'm not sure that 3 months from now will be any safer, and if anything, I think it might be less safe -- hypervigilance may have worn off, we may have retaliated militarily by that time, etc.
Also, keep in mind that basically going to any place where there is a large gathering of people is potentially dangerous -- shopping malls, large sporting events, etc. How much are you willing to change your way of living right now?
