The Minnesota Department of Natural Resources has upgraded its fleet of firefighting aircraft — and not a moment too soon.

More than 91 percent of the state has been in the midst of a moderate drought, due largely to the lack of snowfall this winter. In addition, there are small areas in the southeastern and far-northern portions of the state that the DNR considers “abnormally dry.”

Enter six Fire Boss single-engine air tankers ready to combat the wildfires sparking across the state at the moment.

The DNR sold off two aging CL-215 Bombardier planes for $1.2 million recently, and is now leasing the smaller, more-efficient airplanes from Aero Spray of Appleton, Minn.

The 1970s-era CL-215 planes were “impressive machines,” but they were operating with engine technology inspired during World War II,” said Paul Wannarka, fixed-wing fire operations specialist for the DNR. Maintenance and upkeep of the old warhorses, which are no longer manufactured, proved too inefficient to continue.

The single-engine air tanker Fire Boss planes, four of which have floats that skim the surface of lakes to collect their water supply, were put to use immediately to combat the dry conditions throughout the state, Wannarka said.

Just last week, Gov. Mark Dayton signed an executive order calling for the Minnesota National Guard to aid the DNR in these firefighting efforts.

The Fire Boss planes are manufactured by Fire Boss LLC of South St. Paul and Texas-based Tracktor Inc. Because they are leased, the state doesn’t have to worry about maintenance or hiring pilots.

It’s unclear exactly how much the leases will cost on an annual basis, since the contracts depend on how often the planes are actually used. But Wannarka estimated the Fire Boss fleet will cost about $600,000 less than the $3 million that was set aside to own and operate the CL-215 aircraft.