Flight data

​The first-ever air collision was in 1910, during an air show over Milan. Both pilots survived. The first fatal collision was recorded two years later, involving two military aircraft. In 1922 occurred the first fatal collision of two airliners, about 100 km (70 miles) North of Paris, in difficult weather conditions. Nowadays, the rate is somewhere around 3-4 accidents per 1 million departures, continuously decreasing since 1970. The air traffic is by far the most regulated transportation service.

The air-traffic control is a ground based service meant to make air transportation safer, more efficient and cost effective, while reducing pollution. Which sounds right, but in reality the business is driven by the need to squeeze as much traffic as possible in the limited amount of air space available. Usually, it's a governmental agency providing the service (for example FAA in USA). Sometimes, is a private not-for-profit company (as in the case of Canada), heavily regulated by a government department. The users of the service are the airliners, mostly. They pay fees, depending on the flight length and weight, which are spent to install/upgrade/maintain the navigation aids and ground systems as well as employ and train the staff.

Let's do a bit of math. Say that we have two aircraft 50 miles away, flying at the same altitude on trajectories converging at 90 deg. If each aircraft has a speed of approx. 500 knots (nautical miles/hour) it takes less than 5 minutes until they reach the closest point of approach. You may be surprised to learn that none of the pilots is aware they are heading into trouble, until the last 30 secs or so, because the computers onboard have no information of the traffic around. Way too much data to upload! Without a controller monitoring the traffic, the best case scenario would be a near miss; the worst a mid-air collision.

Now, if you are the one in charge of that controlled airspace, by now the visual alerts are red and blinking on your screen and pretty soon a loud beeping will bring the supervisor behind your chair. Keep calm! you have a coupe minutes to prevent the collision by changing the trajectory of one of the flights. If you are lucky, there might be room for one of them to safely go above or below the current altitude. If not, you must decide which one can reduce the speed and/or deviate from the route. A situation when the aircraft come closer than the required separation minima is an "incident" (to be reported, investigated and lessons learnt) and should not happen. The traffic should be sorted out way before.

To allow a clear description of each flight intent, the airspace is organized into a network of airways, which are corridors connecting two 2D locations (latitude/longitude). The route which the pilot intends to fly between the departure and the arrival airport is a 4D trajectory, specified as a sequence of airway segments with the altitude and speed at the beginning of each segment. In addition to the route, the ICAO regulations require the pilot/airliner to specify details of the avionics onboard (mainly the navigation aids and means of communication), the quality of which allows to determine a level of confidence regarding the aircraft ability to stick to the route. The lower the confidence, the further apart should be keep the other aircraft.

This collection of data (route plus avionics) is the "Flight Plan" and is filed for every single aircraft hours before departure. The flight plan becomes alive when the aircraft is cleared to leave the gate. Subject to various rules and communication protocols, this data begins a journey within a network of ground computers, being augmented and updated as the flight progresses. The air traffic controllers rely on this flow of data in the time-space network of flight plans to create a strategy that would work for a given sector of airspace. Not all aircraft are going to fly at the intended altitude and maybe not even on the preferred route; some of them will burn more gas or be delayed, but they will arrive safe. Unless shit happens!

Next time you go to pick someone from the airport, you may want to use FlightRadar24 to monitor the flight as it approaches and get the estimated time of arrival. You can also see when the aircraft touched down the runway and send a welcome message, right before they turn on the cell service. 😉