An airport delay is a situation in which the departure or arrival of an aircraft at an airport is delayed. This can be caused by a variety of factors, such as weather, air traffic control, mechanical issues, or other operational issues. The term 'airport delay' can also refer to the length of time that a flight is delayed. In this case, the answer to the crossword puzzle is LINE, which refers to the lines of aircraft waiting to take off or land at an airport. These lines can cause delays due to the amount of time it takes for each plane to take off or land.