On April 17, 1944, on Holy Saturday, 350 American and British bombers dropped about 2,500 bombs on Sofia shortly before noon. According to eyewitnesses, "mine surprises" were also thrown along with the bombs. On Holy Saturday, 128 people were killed and 76 were injured in Sofia alone. 749 buildings were destroyed. The air defense of Sofia fired 3062 shells and downed 9 bombers.

Although in small numbers, the Bulgarian fighter pilots managed to shoot down 15 more heavy bombers and showed that the Bulgarian fighting spirit cannot be broken. Lieutenant Nedelcho Bonchev was one of the aces in the sky and managed to down a B-24 "Liberator" by ramming his plane into it. This is the second similar case in the history of Bulgarian aviation, after the feat of Captain Dimitar Spisarevski. However, Lieutenant Bonchev managed to save his life shortly before the collision.

• 106 years since the birth of Captain Dimitar Spisarevski

That evening before midnight, about 30 planes attacked Plovdiv and the region. There were also air attacks on villages in Dobrudzha. The 6-month long bombardment failed to force Bulgaria to capitulate, but instead provoked anger against the Allies.