59 FR 17450, No. 70, Apr. 12, 1994
SUMMARY: This final rule amends part 91 of the Federal Aviation Regulations
(FAR) to provide for the issuance of temporary flight restrictions on certain operations when accurate altitude information is not available. The rule is
warranted because barometric pressure higher than 31.00 inches of mercury (inHg) (1049.8 millibars) exceeds the capability of standard aircraft pressure altimeters and prevents the display of accurate altitude information. The rule provides restrictions on certain flight operations
during periods of abnormal atmospheric pressure conditions and is necessary to promote flight safety during certain operations for which accurate altitude information is critical.
EFFECTIVE DATE: May 12, 1994