President Trump likes to prod the members of NATO about their military spending, which he considers too low. But up high, the defense bloc maintains a robust "air police," with armed fighter jets on round-the-clock standby in Europe to counter the threat from Russia to the airspace of member states.

NATO jets have had a number of high-profile encounters with Russian warplanes, as recently as January, when a pair of Tu-160 Blackjack nuclear bombers were intercepted by Royal Air Force (RAF) Typhoons as they approached British airspace.

The RAF says this follows a pattern of aggression by Russian jets.

"When the Russians do this, they don’t follow a flight plan, they don’t speak to air traffic control," said Glyn, an RAF Squadron Leader whose surname was withheld for security reasons. "There is always that risk that they could have an accident or get close to another aircraft."

The RAF is one of 19 NATO member countries with warplanes on standby in Europe, in what those air forces call Quick Reaction Alert.

The UK's Ministry of Defense says its fighters have been launched an average of eight days a year to meet Russian aircraft in the past decade, but it won't specify exactly how many Russian jets were intercepted, citing national security concerns.

Colonel Eric Moses, the senior U.S. officer at a base in Uedem, Germany, which controls Northern Europle, told VICE News the chances of an incident between NATO and Russian aircraft are still low, "as long as all sides maintain proper, professional, predictable peacetime behavior."

This segment originally aired July 17, 2018 on VICE News Tonight on HBO.