After the briefing, flight attendants inspect the aircraft, ensuring the safety equipment is in place and working properly. If a piece of equipment, such as a fire extinguisher, is found unserviceable, flight attendants must replace the item prior to takeoff. Once passengers are called to board, flight attendants assist with the boarding process. They aid any special needs passengers, children, or VIPs to ensure they receive the proper care while boarding. Tickets and seating positions are verified, and attendants check for both accuracy and possible fraudulent or stolen tickets. Attendants also monitor passengers; they are trained to detect suspicious behaviour and evidence of malicious intent, to prevent hijacking or terrorism. In addition, they help passengers load carry-on baggage, checking that each adheres to aircraft or airline size and weight restrictions.