The FAA oversees aviations regulations part 61 which concerns the certification of pilots, private and commercial, flight instructors, and instructors on the ground. Part 61 is only one of the thousands of regulations, sub-regulations, and addendums regarding the aviation industry in the United States. Airline regulations pass ruling on many different elements of air travel. For example, Part 23 is a discourse on how fit an individual airplane is to fly. This regulation even includes the type and amount of fire retardant used on airline seating. The Federal Aviation Administration frequently revisits each aviation regulations part. With the heightened security after September 11, 2001 the FAA imposed many new regulations having to do with passenger security measures. These regulations were instituted to insure the safety of pilots, air crew members, passengers, airport personnel, and the general public. Passengers will first notice the new regulation upon check in when they are asked for a photo identification. Next, when going through security many items that were previously allowed are no longer considered safe and cannot be carried on by boarding passengers.