WWII - P-38 Lightning

The P-38 Lightning introduced a new dimension to American fighters – a second engine. The multi-engine configuration reduced the Lightning loss-rate to anti-aircraft gunfire during ground attack missions. Single-engine airplanes equipped with power plants cooled by pressurized liquid, such as the North American P-51 Mustang, were particularly vulnerable. Even a small nick in one coolant line could cause the engine to seize in a matter of minutes.