On a wing and a prayer
This expression describes a desperate, dire situation where one can only rely on hope and prayer. It was coined by American songwriter, Harold Adamson, in 1943 in the WWII song Comin’ in on a Wing and a Prayer. The song was about a bomber crew limping home in a badly damaged aircraft after a bombing raid on Germany. It was an immediate hit on both sides of the Atlantic and the phrase soon passed into the language.