Under what condition are certain portable electronic devices prohibited on aircraft?

Portable electronic devices are specifically prohibited on aircraft under Instrument Flight Rules (IFR) primarily due to the potential for interference with the aircraft's navigational and communication systems. During IFR operations, aircraft often rely on precision instruments and systems that could be disrupted by the emissions from portable devices, leading to increased risks during flight.

In contrast, when flying under Visual Flight Rules (VFR), pilots have more visual references and might not rely as heavily on electronic systems, although certain restrictions still apply. While there are general guidelines about the use of portable devices in aviation, the strictest prohibitions usually pertain to IFR conditions, where the safety margin pertains directly to reliance on instrument navigation and communication. This understanding highlights the importance of maintaining the integrity of systems critical for safe flight operations, especially in instrument conditions.