How many feet high n the sky can a jet fly at the highest........?

Question

How many feet high n the sky can a jet fly at the highest........?

Answer 1

When the SR71 was flying it cruised at 75000ft roughly.

The U2 flies its missions routinely over 50000ft.

Most commercial jets cruise at 33000-37000 ft.

Answer 2

Very high if you are pressurized and getting breathable air.

The "Man High" project, a long time ago, lifted a guy up so high with balloons and he wore a pressure suit.  He was the first human to see the curvature of the Earth with his own eyes.