Last week, a drone reportedly hit an Airbus A320 on approach to London’s Heathrow Airport, but so far, there have been no officially confirmed drone strikes involving U.S. aircraft. However, witnesses have told AVweb that a drone did hit a hot-air balloon in flight, during a festival in Vermont in July 2014, causing damage to the fabric envelope. The pilot had just launched, and was about 150 feet off the ground. He landed immediately, and nobody was hurt.
Source: avwebHot-Air Balloon Damaged By Drone