What causes a plane to declare an emergency, and how often does it actually happen at busy airports like Gatwick?

An aircraft declares an emergency, known formally as declaring a "Mayday" or the slightly less urgent "Pan-Pan," for a wide variety of reasons ranging from the genuinely life-threatening to relatively minor technical issues that pilots and airlines treat with appropriate caution. The most common causes include medical emergencies involving passengers or crew, hydraulic failures, engine problems, smoke or fire indications in the cabin or cockpit, landing gear malfunctions, fuel concerns, pressurization failures, and bird strikes that damage engines or airframes. Pilots are trained to err on the side of caution, so even a warning light that might ultimately prove to be a false alarm will often prompt a declaration simply because it triggers a specific checklist that requires priority handling from air traffic control. The philosophy in aviation is that declaring an emergency costs nothing in terms of pride or paperwork compared to the consequences of not declaring one when it was genuinely needed. The process itself is fairly straightforward. A pilot broadcasts on the emergency frequency 121.5 MHz or on whatever frequency they are already using, states the nature of the problem, their position, altitude, and intentions. Air traffic control then clears airspace around the aircraft, alerts emergency services at the destination airport, and gives the crew priority routing and handling. At busy airports this can mean other aircraft are held in holding patterns or their approaches are delayed to give the emergency aircraft a clear path. Ground crews including fire engines, ambulances, and sometimes specialist rescue teams position themselves along the runway as a precaution even if the crew believes the situation is manageable. At a busy airport like Gatwick, which handles around 280,000 aircraft movements per year and is one of the most intensively used single-runway airports in the world, emergencies are declared with surprising regularity. Industry estimates and data from aviation safety bodies suggest that a major hub airport might see anywhere from several hundred to over a thousand declared emergencies annually when you include all categories, though the vast majority are precautionary rather than catastrophic. Many of these are medical diversions where a passenger has suffered a heart attack or stroke and the crew declares an emergency to get priority landing clearance quickly. Others are what the industry calls precautionary landings where a technical warning has appeared and the crew wants to get on the ground promptly without necessarily believing the aircraft is in immediate danger. True full-blown emergencies involving structural failures, complete engine losses, or uncontrolled fires are comparatively rare but do occur several times a year across the global fleet. What the public rarely appreciates is how well the system handles these events. Because pilots declare emergencies relatively freely and early, problems are caught and managed before they escalate. The vast majority of declared emergencies result in completely uneventful landings where passengers might not even be aware anything was wrong, or they might notice fire trucks following the aircraft down the runway as a precaution. The fire trucks and ambulances are positioned not because a crash is expected but because regulations require their presence whenever certain categories of emergency are declared. This can look alarming to onlookers or people watching flight tracking websites, but it is standard procedure designed to ensure resources are immediately available if needed. The frequency of emergencies at Gatwick specifically is not always publicly reported in granular detail, but Freedom of Information requests to the Civil Aviation Authority and reporting from aviation journalists have shown that the airport handles multiple declared emergencies every week when you count all categories. This is not a sign that flying is dangerous but rather the opposite. It reflects a culture where crews are empowered and encouraged to use the emergency declaration system as a tool for getting help and priority handling whenever there is any doubt. The overall safety record of commercial aviation remains extraordinarily good precisely because this precautionary culture is so deeply embedded. Statistically, a passenger flying regularly for decades is extremely unlikely to experience a genuine life-threatening emergency, even though the aircraft they travel on may have declared precautionary emergencies several times during its operational life for reasons that were ultimately resolved without incident.