[crz]

It leaked like a bucket with holes in it. Until it got up in the air/inner space and heated up.
But it make a person wonder what the hell Kelly Johnsons vision was for future aircraft. A aircraft that could go that fast, and so advanced built way back then? When the technology wasn't available they way it is now?

[Busko]

It leaked because the plane’s skin and air framing would expand when flying at those incredible speeds, so if it was tight fitting it would buckle and cause problems.