Hinted by the terrestrial massive Multiple Input Multiple Output (MIMO) communications, a massive MIMO system for Air-to-Ground (A/G) communications is proposed, i.e., due to the aviation environment, multiple Ground Stations (GS) are organized to support the moving air interface for civil aircrafts with the full-band access. The aircraft can access the system with the massive MIMO antenna arrays facilitated in multiple GSs without handover. Compared with the traditional A/G MIMO scheme, not only the system capacity is enlarged, but also the variance of the capacity is greatly mitigated.