NTSB has 494 items for "engine fire" from 1962 to present.
It includes helicopters, foreign flights, pretty much every investigation they have done involving an "engine fire" since 1962.
Most engine fires happen on the ground at startup. The number of mid air fires is considerably less than the 494 investigated here.
According to IATA, in 2017 the estimated number of commercial flights is 36.8 million, not including private, business and military aviation. More than 100,000 PER DAY.