This is footage of a 2016 drone swarm test conducted by the US at China Lake, California. The Perdix Swarm Demonstrations and testing proved that these swarms could be dropped by aircraft at speeds up-to Mach 0.6 and at temperatures as low as -10 degrees C. These drones, specifically, were designed for aerial surveillance, though more applications would undoubtedly be evaluated (such as explosive payloads). 103 drones are dropped from three F/A-18's, converging on their final target a few minutes later.
Each individual drone is not controlled in itself but instead it shares a collective, distributed "brain," travelling in leaderless "swarms," members of which can adapt to changes in drone numbers and remain coordinated with their counterparts.