Many years ago (the 60's) I watched a movie that depicted the trials and struggles of breaking the sound barrier, it was a movie and not a documentary.
There were rocket powered speed sleds that I recall, it was in color and the location was mostly on a Military base.
Seems it was called "90,000 Feet Into the Blue" or similar but searching that and variations of that turns up nothing.
Would love to locate it to watch again.

Any of you remember this movie and/or shed any light on the actual name?

Thanks
Ken