The Federal Aviation Administration said the plane crashed about 5:15 p.m. as it was departing for Honolulu from Louisville’s Muhammad Ali International Airport.
Another article from the AP on it: https://apnews.com/article/ups-cargo-plane-explosion-louisville-deaths-af12da7f8611bad0bf0cb664de189250
The reason it blew up so big was because it was headed to Hawaii, and had 38,000 gallons of fuel on board, basically a full load. That much jet fuel then burned, making the fireball.