From personal experience, I can say No, infrared is unaffected. I took some Kodak HIE with me to Cambodia, and it went through the xray machines in Singapore, Cambodia, Singapore again, Amsterdam, New York, and Washington DC with no ill effects. If it can survive xraying in a third-world country with old machinery, plus all those other xrayings, not to mention the cosmic ray bombardment all film gets on the plane (which is a greater radiation exposure than all the xraying it is going to get on the ground anyway), it isn't going to be affected. If you have extremely high-speed film (800+), bring the lead bag to help with exposure at altitude, and get a hand-inspection at the airport.