Editor's note: Alfred Yeo is currently an Aerospace Engineering postgraduate student at the University of Illinois, Urbana-Champaign.

The news of Malaysian Airlines Flight MH370 disappearing while en route from Kuala Lumpur to Beijing has come as a real shock to all of us. Our thoughts and prayers continue to go out to the everyone on that flight.

One may ask, how can a 300 tonne aircraft, the length of 5 school buses, simply disappear without a trace? To answer this, we must first understand how aircraft are tracked by the Air Traffic Control (ATC).

How are aircrafts in the sky tracked?

ATC has two primary modes of determining where an aircraft is. The main mode of tracking is referred to as the Secondary Radar, where an aircraft beams out a signal using a transponder. This signal indicates to controllers the exact location, the identification of the aircraft, and its altitude.

Secondary radar only picks up aircraft equipped with transponders. If the transponder is switched off or non-functional, the plane will not appear on the controllers screen. At this moment we do not know what happened to MH370's transponder.

The hijackers of all 4 flights in the 9/11 terrorist attack had turned off the aircraft transponders, making it difficult for controllers to locate and track the planes. Coupled with the confusion caused by the “fog of war”, American Airlines flight 11 and United Airlines flight 175 had ploughed into the World Trade Centre, and American Airlines flight 177 into the Pentagon, before fighter jets could scramble to intercept them.

The other form of tracking is referred to as the Primary Radar. Primary radar is very similar to the types of radars we see in a 1990s submarine war movie. A constantly rotating radar will pick up any large metal object in the sky and show up as a green dot on the controllers screen. Information like type of aircraft, speed, or altitude is not known.

Why didn’t the pilots call for help?

All pilots are trained to first and foremost “fly the plane” during an emergency. It is essential that pilots regain control of the aircraft before doing anything else. This can sometimes be much harder than imagined.

Take for example Air France Flight 447, the last plane to vanish before MH370. It was flying from Rio de Janeiro to Charles de Gaulle when it crashed after it hit turbulence over the Atlantic in 2009. An iced over pitot system misled its pilots in their reading of the aircraft's speed which resulted in the them pulling the nose up too high and stalling the aircraft. The pilots never got a chance to call for help.

Parts of the Air France 447 wreckage. Source: Airfacts Journal

How is the search and rescue operation conducted?

Aside from the visual identification of a wreckage, all commercial flights have a “black box” that is equipped with an “Underwater Locator Beacon”. This device pings out an ultrasonic pulse once a second, audible to the human ear, and can be picked up easily by sonar. The beacon is designed to send out signals for 30 days. After this time, the locating of any lost aircraft at sea will become much harder.

Why hasn’t the plane been located?

While a Boeing 777 is a fairly large machine, it must be understood that the aircraft could have broken up into many pieces up at 30,000 ft and the wreckage being spewed over tens of square kilometres. Furthermore, the Gulf of Thailand spans 320,000 km². That is approximately 450 times larger than Singapore. This is also assuming the aircraft went down around its last known position. Theoretically, the aircraft had the capability to fly an additional six hours without being on the ATC's radar.

Trying to locate the aircraft, whether it is still intact or disintegrated, is equivalent to trying to locate confetti thrown off the top of Marina Bay Sands into the Bay area.

However, it is heartening to know countries have set their differences aside and come together to help in this time of tragedy. With 9 nations, 40 ships, and 34 aircrafts, I believe the plane will be found soon and there is always hope of finding survivors aboard MH370.

Similar Past Incidents

Adam Air Flight 574 had experienced navigational difficulties while flying domestically over Indonesia in 2007. Due to faulty equipment, the plane had accidentally flown into bad weather. The plane was old and had a tendency to roll to the right. As a result of this, and poor handling of the plane by the pilots, Adam air had entered a deep stall and crashed over Sulaweisi. The aircraft was only located 10 days later by a fisherman.  No emergency calls were made by the pilot.

Silk Air Flight 185 crashed over Sumatra, Indonesia in 1997. After a 3 year investigation, no conclusive cause of the accident was found. It is speculated that the pilot had committed suicide. No survivors were found.

Air France Flight 447 was en route from Brazil to France in 2009 disappeared over the Atlantic Ocean. Turbulence, an iced over pitot system giving the pilots wrong airspeed data, and pilot error were blamed for the crash. The black box of Flight 447 was only found 2 years after the crash. No radio calls were made.

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