Dutch pilot Christiaan van Heijst's photographs capture the views he sees from his cockpit.
From the patterns made by the Marho Kotri River Delta in Pakistan, to the amazing colours of the Aurora Borealis over Alaska, his images show a point of view not usually captured.
Although van Heijst does not take photographs on every flight, spending up to 100 hours in the air a month means he can find time to work on the aerial photography he has spent more than a decade perfecting.
Often, he will just place his camera on the cockpit's glareshield with the lens next to the window, allowing it to sit there during a long exposure. However, the pilot observes: "I still have to shoot at least five to 10 images at night with long exposures to get at least one very sharp one, if I'm lucky."
Van Heijst often works on long haul flights where three or more pilots are flying the plane, giving him the opportunity to move about and make images such as this one of the Northern Lights over the wing of a Boeing 737. He explains that the lights are so bright that sometimes he only needs an exposure of a couple of seconds to capture them.
This photograph was made over northern Russia and sees a faint show of the Northern Lights alongside the sunrise. Taken in near darkness, the long exposure records the lights and rising sun.
Using exposures as long as 30 seconds, the photographs are at high risk of blurring - particularly with the constant threat of turbulence. In fact, van Heijst jokes: "I found out that Murphy's law (an adage that states, anything that can go wrong, will go wrong) applies in the stratosphere as well; the moment I position my camera, the aeroplane starts to shake and tremble."
The image below of a storm over Toronto, Canada, was taken whilst van Heijst was a passenger on a flight. Using a fisheye lens, he created the illusion of the camera being outside the plane, contrasting human machinery with natural weather conditions.
The final image, of a sunset over the Himalayan mountains, leads the pilot-photographer to say: "Seeing views like these makes me realise how privileged I am in this job and position."
All photographs taken by Christiaan van Heijst.