A ramp worker reported they forgot to chock the wheels of the belt loader and it rolled into the aircraft.

Narrative

While on the last flight of our teams day. Moving fast rushing we were short handed and getting to make it back to ZZZ with out missing our flight. We had a down load flight ABC. I was the back belt loader. once I drop my safety cones in the circle of safety; I had pulled up to the pit with my belt loader. Then taking it out of gear; pulling up the E brake making sure it's in park. Once I had the belt loader set; I had crawled into the pit. As I sat in the pit; I started scanning a couple bags with two of my court right outside one at the end of the belt; offloading the bags; and on the side of the outside pit scanning bags. We were able to start downloading bags. But once we realized time wasn't on our side; my coworker; Person A; had come up to the two switches in the front of the belt. After down loading a couple bags; my co worker walks to the two switches to either go forward in gear or speed up the belt. Person A had pushed the belt speed switch up to high - The [other] switch got pushed with the speed switch; making them both activate. As I looked down towards the belt and Person A; I noticed the belt loader wasn't chocked so it decided to go forward hit the plane and ride under it. Luckily no one got hurt; but there was damage on the plane and belt loader. I am truly sorry for this incident happening. I have learned from this mistake to always be cautious once I'm in the circle of safety and work as safety as possible on the line. I've learned a lot from this experience and know I must always follow and double check that I'm setting up my belt loader for up loads and own loads right.