In aviation, instrument meteorological conditions are weather conditions that require pilots to fly primarily by reference to flight instruments, and therefore under instrument flight rules, as oppose
A pilot's view of the runway just before landing in thick fog at night
Summary of United States VMC minima (14 CFR 91.155), providing requirements for minimum visibility and separation from clouds for different airspace classes. In this example, for airspace classes C/D/E up to an altitude of 10,000 ft (3,000 m) AMSL, whether day or night, VMC minima require 3 miles (5 km) of visibility (denoted "3 SM") and cloud clearance of 1,000 ft (300 m) above, 500 ft (150 m) below, and 2,000 ft (610 m) horizontally ("152").
Human senses are not naturally geared for the in-flight environment. Pilots may experience disorientation and loss of perspective, creating illusions that range from false horizons to sensory conflict
Blind flying. The pilot wears goggles blocking the colors transparent through the orange plastic sheet in front of him. The instructor wears no goggles and so has an outside view tinted orange.