Flights can be cancelled for a number of reasons ranging from weather to technical issues. Poor weather conditions such as high winds, low visibility, or thunderstorms can make it too dangerous to take off or land, resulting in flights being cancelled. Additionally, mechanical issues with the aircraft, air traffic delays, and crew shortages can also result in cancellations. Flight crew reaching their time limits for duty time is another source of cancellations. Finally, airport closures due to security or maintenance issues can prevent flights from departing or arriving.