The CH-47A Chinook tandem-rotor, heavy-lift helicopter entered U.S. service in 1962. Over its long service, the Chinook has seen many derivative variants and undergone numerous improvements, including more powerful engines, additional armor, and equipment for special forces operations. Modernization programs updated MH-47D and MH-47E aircraft and upgraded them to MH-47G Chinook Special Operations Aviation (SOA) helicopters, finishing the project in 2015. This means those Chinooks have been upgraded with advanced avionics, including a digital Common Avionics Architecture System (CAAS). Boeing announced the production of MH-47G Block II in 2020 with a goal to eventually deliver 69 of them. MH-47G Chinooks have inflight refueling capabilities and defensive and adverse-weather piloting aids, and they are armed with two M134 miniguns and two M240 machine guns.