The U.S. Forest Service has 18 large air tankers on exclusive use (EU) contracts this year. In 2020 the agency started out with 13 on contract in April and May but by June 24 had added 11 on modified call when needed (CWN) contracts for a total of 24. Modular Airborne FireFighting Systems C-130 aircraft from the National Guard and Air Force Reserve were deployed from July 23 until October 4 in 2020, usually two at a time. The dates they will first be on duty could change if the Forest Service decides they need to come on early, but the scheduled 160-day “mandatory availability periods” (MAP) which are different for every air tanker specify that two will begin in March (11th and 17th) and most of the rest will start in April and May. The MAPs end August 18 through November 20 for the 18 aircraft, but those dates could be extended if necessary.