Just one!
:o
An old favourite then. It has resided on the small 'specials' shelf for many, many years - nestling amid an eclectic bunch of fellows.... as I recall, it starts something like this:
...The vibrating clangour from the four great piston engines set teeth on edge and made an intolerable assault upon cringing eardrums. The decibel-level, Smith calculated, must have been about that found in a boiler factory, whilst the shaking cold in that cramped, instrument-crowded flight-deck was positively Siberian in nature. On balance, he reflected, he would have gone for the Siberian boiler factory any time, since, whatever its drawbacks, it wasn't liable to fall out of the sky or crash into a mountainside, which in his present circumstances seemed a likely enough, if not imminent contingency, for all that the pilot of their Lancaster bomber appeared to care to the contrary...
Smith, Schaffer, a triple-cross, the Bavarian Alps, Schloss Adler, cable-cars, a wickedly dry turn of phrase... and Alistair MacLean creates an adventure story that for me has never lost its lustre.
'Where Eagles Dare'