The agriculture ministry said two amphibious water-scooping aircraft were sent to help dowse fires in the northern region of Cantabria and another plane was dispatched to the central region of Castile and Leon.
The regional government of Cantabria said firefighters were battling 25 blazes while the government of the neighbouring region of Asturias in northwestern Spain said 16 wildfires were burning in its boundaries.
A helicopter battling a fire in Asturias crashed , killing the pilot and sole occupant of the aircraft.
Forest fires are unusual in December in Spain but low rainfall and a warm autumn have left much of the country vulnerable to blazes.
Wildfires have destroyed more than 54,000 hectares (13,300 acres) of agricultural and forest land in Spain this year, exceeding the area burned over the previous two years combined, most of it in major summer fires, according to agriculture ministry figures.