(1) IFR is where the pilot is ultimately responsible for navigation, obstacle clearance and traffic separation using the see-and-avoid concept. The vast majority of commercial traffic (any flight for hire) and all scheduled air carriers operate exclusively under IFR. However, commercial aircraft providing sight seeing flights, aerial photography, or lift services for parachute jumping usually operate under VFR. So the answer is No. (2) VFR flight is not allowed in airspace known as class A, regardless of the meteorological conditions. Class A airspace begins at 18,000 feet msl, and extends to an altitude of 60,000 feet msl. However, CVFR flight is used in locations where aviation authorities have determined that VFR flight should be allowed, but that ATC separation minimal and guidance are necessary. (3) Meteorological conditions that meet the minimum requirements for VFR flight are termed visual meteorological conditions (VMC). If they are not met, the conditions are considered instrument meteorological conditions, and a flight may only operate under IFR. However, as mentioned in point (1) above, all class A flights are IFR regardless of the weather conditions. So that's correct.