The Greek Company 3D S.A. operates 2 Piper Cheyenne II aircraft, that have been equipped with a weather modification kit. Anotec was contracted to obtain the noise certificate for this modification under ICAO Annex 16 Chapter 10 regulations. Flight tests were performed in Kastoria (Greece) with our mobile test equipment. Our pilot guidance system was used to accurately fly the required flight path. Data analysis was performed with our approved analysis software CEDRA and results were reported to EASA. The noise certificate was obtained from EASA within a month after the flight tests.