Which of the following is NOT typically a requirement for IFR flight?

The correct answer is clear weather conditions, as this is not a requirement for IFR (Instrument Flight Rules) flight. IFR flights are designed for operations in various weather conditions, including low visibility and cloud cover. This allows pilots to navigate and operate aircraft safely without relying on visual references outside the cockpit.

In contrast, filing a flight plan with ATC, maintaining a minimum ceiling and visibility, and having the appropriate instruments and equipment onboard are all essential requirements for IFR flight. A flight plan ensures that air traffic control is aware of the aircraft's intentions and can provide necessary separation and guidance. Adhering to the minimum ceiling and visibility standards is crucial for safe flight operations, even when flying on instruments. Moreover, having the appropriate instruments and equipment is a fundamental requirement for a pilot to safely navigate and control the aircraft under IFR conditions.

Thus, clear weather conditions are not a prerequisite for IFR flight, making this option the correct choice.