Wildlife collisions with U.S. civil aircraft (hereafter incidents) pose safety and economic concerns. Terrestrial mammals represented only 2.3% of wildlife incidents, but 59% of these incidents caused damage to aircraft. I examined 2,558 incidents in the Federal Aviation Administration (FAA) National Wildlife Strike Database to characterize and analyze overall mammal incidents by airport type, emphasizing white-tailed deer (Odocoileus virginianus) and bat incidents with U.S. civil aircraft. Mammal incidents caused 5 times greater damage than other wildlife which varied by airport type and appeared associated with species’ behavior. I provided relative hazard scores to determine which species were most hazardous to aircraft. Relative hazard increased with increasing body mass with mule deer (O. hemionus), white-tailed deer and domestic dog (Canis lupus familiaris) most hazardous to aircraft. White-tailed deer caused 6 times greater damage than all other wildlife and are hazardous to aircraft. In contrast, bats posed a low hazard to aircraft.