What causes a change in flight conditions from VMC to IMC?

A change in flight conditions from Visual Meteorological Conditions (VMC) to Instrument Meteorological Conditions (IMC) occurs when visibility becomes restricted, particularly when it drops below 3 miles. VMC indicates that pilots can fly using visual references outside the aircraft, while IMC signifies that visual references are insufficient for navigation and control, requiring pilots to rely on instruments.

When visibility drops below 3 miles, pilots may encounter fog, heavy rain, or other weather phenomena that impair their ability to see and rely on visual cues. This operational change necessitates adherence to instrument flight rules (IFR) since visual navigation is no longer safe.

In contrast, a ceiling rising above 1000 feet or improved weather conditions would likely indicate a transition from IMC back to VMC. Additionally, flight altitude exceeding 5000 feet does not inherently indicate a change to IMC or VMC; the primary factor is the visibility and cloud cover encountered at that altitude.