When navigating on the airport surface, aircraft ground position and ground velocity can be estimated using a large variety of sensors, such as Global Navigation Satellite System, Inertial Navigation System, Wheel Speed Sensors and others. The largest contributing sensor is the GNSS, but measurements from this sensor are affected by signal blockage and multipath. In [Che10], a GNSS multipath simulator for airport navigation has been proposed. In this multipath simulator, up to now, a far-field aircraft+antenna radiation pattern has been used. It has been obtained from measurements at L1 frequency on one scaled aircraft. This means that for different antennas and aircraft, the range errors predicted by the simulator may lose validity. Moreover, the validation of this multipath algorithm has not been fully assessed. The antenna gain pattern used under the multipath simulator is first improved. To do so, a GPS L1 antenna combined with the aircraft structure of the Airbus aircraft family are simulated with an electromagnetic commercial software. For each antenna and aircraft model, the analysis relies on simulations with the electromagnetic software Feko and comparisons. These comparisons show that the different aircraft models have a similar far field gain pattern in accordance with the measurements. Then we propose a validation of the GPS multipath simulator for GPS L1 C/A signals. This is achieved through the comparison of simulated multipath errors with the multipath errors estimated from real data measurements. The extraction is obtained by means of a Code Minus Carrier (CMC) algorithm coming from a previous AIRBUS/ENAC collaboration in 2012. A number of 52 flights are considered for this validation. By comparing the L1 C/A multipath error variances on a restricted area of Blagnac airport for an elevation bin, we may assess such validation.