  The influence of the geomagnetic field on the development of air showers is
studied. The well known International Geomagnetic Reference Field was included
in the AIRES air shower simulation program as an auxiliary tool to allow
calculating very accurate estimations of the geomagnetic field given the
geographic coordinates, altitude above sea level and date of a given event. Our
simulations indicate that the geomagnetic deflections alter significantly some
shower observables like, for example, the lateral distribution of muons in the
case of events with large zenith angles (larger than 75 degrees). On the other
hand, such alterations seem not to be important for smaller zenith angles.
Global observables like total numbers of particles or longitudinal development
parameters do not present appreciable dependences on the geomagnetic
deflections for all the cases that were studied.
