Mcrit Story...
A 777 was cruising along, everyone FDH, when suddenly an SLF calls the F/A and tells her the wing is bent.
The F/A looks out the window, and behold - the wing is bent.
She ring the flightdeck, a heavy F/O goes back to look, and yes, the wing is bent.
Now the Capt. goes back and has a look, and the wing is still bent.
Everything's normal, no vibrations, normal fuel consumption etc, but since they are close to home base and a long flight ahead of them, they decide to turn back and have that thing inspected.
During descent the wing goes back to normal and on the ground no evidence of it could be found.
They ring up Boeing, and they say:
"yeah, we are familiar with it, it's a shockwave which distorts the vision and makes the wing look bent".
Proving the point: Mcrit is below normal cruising speed for some airplanes.
In fact, any airplane who has a super-CRITICAL wing will have Mcrit below Mmo.
That's why they call'em "super-critical".