The Flak 38 was introduced as a competitor to the 8.8 cm FlaK 18. They encountered heavy flak and continuous fighter attacks. Bremen was guarded by 250 flak guns. German defences (including "FlaK" guns and field guns) eventually stopped the attack. The bullet can just walk through a flak jacket. Cruickshank attacked the U-boat, flying his Catalina through a hail of flak. Their aircraft is hit by flak and catches fire. The Flak 18 was mounted on a cruciform gun carriage. These shields could be retro-fitted on older Flak 18s as well. This was potentially dangerous and exposed them to further risk from flak and night fighters. There are German reports of P-63s shot down by both fighters and flak. The crews faced deadly flak and fighters, particularly Focke-Wulf Fw 190s, which they called "snappers". Flying at put the B-29s above the effective range of Japanese flak. The idea for the flak jacket came from Col. One aircraft was lost to "flak".