Here's another, even bigger, ambiguity in the rules. FAR 91.151 and 91.167 specifically refer to flight in "VFR and IFR conditions," respectively, both in the label and the body text of the rules. In FAR 1.1, which contains the FAA's official definitions of terms used in the rules, "IFR conditions" is defined as "weather below the minimum for visual flight rules." So it appears that a pilot flying IFR, with a clearance, but not above 18,000 feet and in VFR weather conditions, is flying under the fuel requirements of FAR 91.151, which applies to flight in VFR conditions and only requires fuel reserve for the flight plan trip. But if a pilot flying IFR flies into the clouds, then FAR 91.167 seems to apply and he needs a different fuel reserve. Got that?