Final answer:
Pilots flying under IFR in controlled airspace must report any changes or deviations as soon as possible to ensure safe operations.
Step-by-step explanation:
When flying under IFR (Instrument Flight Rules) in controlled airspace, a pilot must report any changes or deviations from their planned route or altitude as soon as possible. This includes reporting any equipment malfunctions, weather conditions, or any other factors that could affect the safe operation of the flight. The purpose of these reports is to ensure that the air traffic controllers have accurate and up-to-date information about the location and intentions of the aircraft, allowing them to maintain separation and facilitate the smooth flow of air traffic.