If you travel more often you may know that some things on board are not free. But if you inform enough, there are some things for free. Here is the list of 8 things. If you know more write in comment.
1. A tour of the cockpit: Many pilots allow children to visit the cabin.
2. Extra snacks: The complimentary snacks offered on flights are tiny and often leave you hungry. Simply ask for seconds — if there are leftovers after all customers have been served, flight attendants will happily give you an extra snack.
3. Basic medications and bandages: The most basic medicine like those on headaches or shooting you can get them for free while flying.
4. You can change the seat: If you ask before, it can happen.
5. Sanitizing wipes: Airplanes are dirty and carry a lot of germs, which is why you want to wipe down surfaces like the tray table in order to avoid getting a cold. If you forget to pack your own sanitizing wipes, ask a flight attendant since they usually have them on hand.
6. Free Alcohol: Many airlines get you a free alcohol, you only need to ask.
7. Useful things: You can ask a set of make-up or playing cards, writing …
8. One more bottle with water: All passengers who have bottle with water before flight, they must splash water but keep the bottle.