Experiencing diarrhea on a plane is a stressful situation that requires immediate management. First, notify a flight attendant discretely; they can sometimes prioritize your access to a lavatory or provide basic medical supplies like rehydration salts. Stick to the BRAT diet (Bananas, Rice, Applesauce, Toast) if food is served, but ideally, avoid eating entirely until you land. The most critical step is hydration; aircraft cabins are incredibly dry, and fluid loss from diarrhea can quickly lead to severe dehydration. Drink bottled water or ginger ale (without ice) and avoid caffeine or alcohol, which irritate the gut. If you have a travel first-aid kit, taking an over-the-counter anti-diarrheal like Loperamide (Imodium) can help slow the symptoms, but consult a professional if you have a fever. For future flights, always pack "traveler's diarrhea" medication in your carry-on and avoid raw fruits or tap water at the airport, as these are the most common triggers for mid-flight gastrointestinal distress.