Taking to the skies has expanded our mobility in extraordinary ways. Journeys that once took days or months now take a matter of hours. Airplanes and helicopters are amazing machines that serve as a testament to the ingenuity and innovation of humanity. To function properly they require tremendous power, speed, and altitude – all of which can create tragic outcomes when mixed with mechanical malfunction, bad weather, or pilot error.

The invention of the airplane opened an entire new front of warfare and reshaped combat forever. Airplanes started out as reconnaissance vehicles, with large scale use in World War I. Over the years they have been modified to shoot down other planes, drop bombs, and deploy paratroopers. (Airplanes are one of the inventions that shaped military history.)

However, military plane crashes have been a part of their use since nearly the beginning of flying. The first passenger to die in an airplane crash lost his life in 1908 when aviation pioneer Orville Wright crashed while showing off the plane he’d built with his brother to the U.S. military. Orville was badly injured and later recovered, but his passenger, Lieutenant Thomas Selfridge, was not so lucky and died of his injuries. However, the accident did not stop military aviation and another model made by the Wright Brothers became America’s first military war plane.

Aircraft have grown significantly safer over the years, with crashes peaking in the 1970s. However, it has taken significant trial and error and development of new technology to make planes as safe as they are today. During World War II, over 13,000 American aviators lost their lives in training accidents.

Click here to see a list of 18 of the worst aircraft disasters in military history

24/7 Tempo has listed some of the worst aircraft disasters in military history. This list isn’t necessarily a complete list of the deadliest military air crashes. Some of the aircraft on this list were operated by private citizens at the time of the crash, but the planes were originally military equipment, and in one case a military plane caused a crash but wasn’t brought down itself.