Blackhawk / CRJ-700 Midair

[Gatordev]

Depending on altitude:

I think he was referring to the the AIM (7-2-3) stating:

...
3. If the difference from the known field elevation and the altitude read from the altimeter is plus or minus 75 feet or greater, the accuracy of the altimeter is questionable and the problem should be referred to an appropriately rated repair station for evaluation and possible correction.

I can't find the regulatory statute that applies a number to operating VFR, as 91.411 applies to IFR flight w/ no minimum deviation and only mentions it must be certified by a repair station. No doubt the repair station utilizes the standard you mention.

But at the end of the day, you could still be 75 feet off (and within 24 months) and still be legal (non-regulatoryly speaking).