A United States Air Force (USAF) F-15 fighter jet travels at low altitude through the “Mach Loop” series of valleys near Dolgellau, north Wales on June 26, 2018. The Mach Loop valleys, situated between Dolgellau and Machynlleth, are regularly used by the military for operational low flying training which can take place as low as 76 metres from the nearest terrain. The USAF regularly use the loop to practice low-altitude flight, which confuses radar systems. (Photo by Oli Scarff/AFP Photo)

The series of shots show the bare steel infrastructure of the Bushfield army training camp near Winchester which was in operation during World War Two and was used to train Royal Green Jackets recruits in the sixties. The spectacular images were taken by an urban explorer who wished to remain anonymous. Here: A railway siding in Wiltshire, UK where ammunition was transferred by tunnel to an underground storage facility. (Photo by MediaDrumWorld.com)

Participants run at the “Half-Naked Marathon” at Olympic Forest park in Beijing, China, February 28, 2016. This annual running event which requires participants to run half-naked, was organized to promote environmentally friendly lifestyles. (Photo by Kim Kyung-Hoon/Reuters)

Kazakh troops march during a parade of the armed forces to mark the Defender of the Fatherland Day in Astana, May 7, 2014. (Photo by Mukhtar Kholdorbekov/Reuters)

Performers dressed as Pikachu, the popular animation Pokemon series character, perform in the Pikachu parade in Yokohama on August 7, 2016. Some 50 life-size Pikachu characters, the most famous from the Pokemon game, marched along the city’s waterfront street as visitors took mobile phone pictures and videos of them in scorching sunshine. Some participants said they attended the event to search for rare characters of Pokemon – a word short for “pocket monster” – for the megahit smartphone app, which was launched in several countries around the world last month. (Photo by Kazuhiro Nogi/AFP Photo)

Enthusiasts gathered at Cad East in Snowdonia National Park, England to take pictures of F-15 Eagle fighters as they completed the Mach Loop, November 2017. (Photo by Caters News Agency)

Military policemen try to open a path ahead for the funeral of 21-year-old Mohamed Adel, one of the army officers who died in yesterday's Sinai attacks, in Al-Kaliobeya, near Cairo, Egypt, July 2, 2015. Egypt launched air strikes on Islamist militant targets in the Sinai peninsula on Thursday, killing 23 fighters a day after the deadliest clashes in the region in years, security sources said. The sources said those killed had taken part in Wednesday's fighting in which 100 militants and 17 soldiers, including four officers, were killed, according to the army spokesman. (Photo by Mohamed Abd El Ghany/Reuters)

Pilots plan a flight manoeuvre with model aircraft at a military air base in Vasylkiv, Ukraine, August 3, 2016. (Photo by Gleb Garanich/Reuters)