Ever wondered what all the smoke was all about?
The smoke you see is the 1700 pounds of water injection used for the Boeing 707s JT engines in those early days.
In fact it is just unburnt fuel/water mix. Injected water cooled the temps enabling more thrust to be generated for take off.
In fact the J57 that powered the B 52 had similar water injected assistance.
Imagine the opposition today if modern airliner's engines caused such pollution.
That was the price we paid then to get into the jet age and it was acceptable.
For the military, anything to get superiority is acceptable.