Security and safety are top priorities in aviation. An airplane must get Pre-Departure Clearances (PDC’s) and IFR route clearance to depart, if any issues occur during the clearance process, to ensure your safety the issues have to be resolved which all of this requires time, thus may cause a delay.
Flights may depart even in bad weather as modern aircraft can withstand even thunderstorms, however during a thunderstorm it is forbidden to refuel or load and unload luggage, as lighting could strike any element present on the runway. Because of the weather at the departure airport, on the way or at the destination, such as snow or rain which obstruct the runway and its vicinity, nobody would risk hundreds of lives and an expensive aircraft for no good reason, and weather delays do occur.
Pilots run final checks right before the flight, and if they see something isn’t safe for the aircraft to fly, they contact the ground crew and fix things together. Sometimes technical failures can be serious and time-consuming to repair; or a special piece is required that is not immediately available. In such cases your flight may get delayed or cancelled.
Waiting for Connecting Passengers, Luggage and Cargo
Connecting flights are the most difficult to handle for obvious reasons: there are two different airplanes that need to adjust their schedules to each other. A flight can sometimes be delayed because of the late arrival of previous flight.
Waiting for Crew
It sometimes happens that their previous flight is not exactly on schedule for some reason, the crew may max out their hours results in the expiration of the crew member’s duty period. Without the enough numbers of qualified crew for the operation, the airplane cannot take off.
Waiting for Catering
Plane food might not be your favorite but it is mandatory, catering line operations is managed by an airline catering agent, and things sometimes don’t go as planned or catering can’t find your connecting plane, the pilot can’t take off until the food is delivered.
WEIGHT AND BALANCE
Manufacturers attempt to make the airplane as light as possible without sacrificing strength or safety. Every airplane has something called maximum takeoff weight (MTOW), if an airplane exceeds that weight, the airplane may be incapable of flight. Operation with the center of gravity (CG) outside the approved limits may result in control difficulty, it could have involved moving you to another seat to achieve proper center of gravity.
AIR TRAFFIC AND AIRPORT CONGESTION
Every year hundreds of near-miss collisions are reported, congestion caused waiting times often extend to hours at major airports. Air traffic delays occur when demand for airports or airspace exceeds available capacity. Airspace and airports are clogged by the rising number of arriving and departing aircraft. Airliners must wait their turn for gates, for ground personnel, for maintenance, and to take off.
EMPLOYEE AND BIRD STRIKE
Airport and airline employees go on strikes almost every year, it’s among the top reasons for flights get cancelled and delayed in Europe. Bird strike mostly happen during takeoff and landing, if an airline is unable to repair or replace the aircraft in time, bird strike can result in delays or cancellations.