No, pilots are strictly prohibited from flying when they are sick under FAA Part 61.53 and similar international regulations (like EASA). The rule states that a pilot cannot act as a required flight crewmember if they have a "known medical condition" that would make them unable to meet the requirements for their medical certificate. This includes minor ailments like a common cold, which can become dangerous in a cockpit due to "ear blockages" during pressure changes, or the side effects of medications. In 2026, airlines have robust "fatigue and sickness" reporting systems that encourage pilots to call in sick without fear of retaliation, as a pilot's cognitive function and reaction time must be at 100% to manage the complex avionics of a modern jet. Even common over-the-counter medications like Benadryl are banned for use before a flight due to their sedative properties. If a pilot becomes ill during a flight, they must declare an "incapacitation" to the other pilot, who then takes sole control of the aircraft to ensure a safe landing at the nearest suitable airport.