Commercial aircraft flights across the North American continent encounter a small radiation exposure (normally <20 ¿Sv) from galactic cosmic radiation. During October and November 2003, there was significant perturbation in the cosmic ray flux near the Earth due to extraordinary activity on the Sun. The associated sequence of solar flares and coronal mass ejections resulted in a significant decrease in the background galactic cosmic radiation levels upon which there were sudden impulsive increases from solar cosmic ray events. These fluctuations in the cosmic ray intensity were detectable at commercial aircraft cruising altitudes and at sea level cosmic ray neutron-monitoring stations. This paper compares the in-flight radiation dose data acquired during the disturbed conditions on 29 October 2003 with the dose data acquired over the same route in January 2004 during quiescent geomagnetic conditions. This comparison shows that during Forbush decreases or ground level cosmic ray increases, the CARI aircraft radiation dose prediction software does not adequately describe the radiation exposure from cosmic radiation.