[Tenacious 1]

Some say that F 86 in steep dive could exceed Mach 1

I was going to comment on the same. I don't know if that was ever proven. But after Chuck made it official, and the implications and symptoms were revealed, it is said that some pilots of the F-86 made that claim. It seems plausible but is worth noting. The F-86 was not designed for that speed and I do not recall the claims ever being affirmed by engineers. I'd be curious to know, however.

[Steely Tom]

F-86 had trailing edge control surfaces on its rudder and horizontal stabilizer; this made it vulnerable to loss of attitude control authority at supersonic speeds due to flow effects resulting from the shock wave that formed leading edges.

The need for full-motion control surfaces was discovered around the time — or soon after — the crash of the de Havilland DH 108 "Swallow" that killed Geoffrey de Havilland in England.

The need for full-motion control surfaces was classified top secret, and was one reason films like this one were not released to the public for many years after the event.

If the F-86 was taken supersonic, it would have been very risky to the pilot. I'm not saying it didn't happen; actually, the sound barrier had been closely approached if not broken by pilots of the P-38 Lightning, when in steep dives, during and immediately after WWII.

[Ol' Dan Tucker]

It seems plausible but is worth noting. The F-86 was not designed for that speed and I do not recall the claims ever being affirmed by engineers.

The F-86E and later models featured an all-flying tail, which is required when flying at supersonic speeds.

Chuck Yeager discovered during the run-up to supersonic flight in the X-1 that the conventional stab/elevator became unresponsive and was unable to control the aircraft in the pitch axis. Long-story short, he used the elevator trim tab, which changed the angle of incidence of the stab in small increments. This allowed him to control the aircraft during the transonic/supersonic phases of flight.

This information was instantly classified as top secret.

When applied to the F-86, this feature allowed it to safely fly beyond the speed of sound. The Soviet MiG-15 did not have an all-flying tail, so it was limited to subsonic speeds.

[YogicCowboy]

Given the swept wing with its delayed onset, courtesy of obtained German research, it is plausible, if:

Adequate altitude.
Manageable buffeting.
Controllable surfaces.

As others have noted, the controllability problem gave rise to the all-flying surface.

If the MiG-15 had had that, I suspect it could have gone supersonic rather easily in a steep, high dive, since it had both the swept wing and a T-Tail that should have minimized elevator turbulence.