Everyone knows that air travel is statistically the safest form of transport, but when things go wrong, disaster looms. Aeronautical engineer Professor Brendan Walker celebrates the unsung heroes who keep us airborne - but warns that modern aviation is too technologically complex to be entirely safe. Plane crashes are mercifully rare - but in today's congested skies, near misses and narrow escapes are anything but. Every day around the world over 100,000 passenger planes take to the air, each flight depending on the careful actions of thousands, from assembly line workers to maintenance staff, pilots, cabin crew and air traffic controllers. Tiny cracks, circuit breaks and any number of computer errors can lead to catastrophe, while flight and land crew must be alert to external forces from lightning and bird strikes, to unexpected turbulence or volcanic eruptions. Combining user-generated content, cabin and control tower audio recordings and archive news footage - including Captain Chesley Sullenberger's heroic 2009 emergency landing of a passenger jet on the Hudson in central Manhattan - this four-part series investigates all the perils and precautions from take-off to landing.