This is the first "Die Hard" sequel since part 2 where a performer (besides Bruce Willis) has reprised their role in an obligatory cameo. Mary Elizabeth Winstead reprises her role of Lucy McClane from "Live Free Or Die Hard". Besides Winstead and Willis, the only other actors to appear more than once in the "Die Hard" films are Reginald VelJohnson, William Atherton, and Bonnie Bedelia (who all appeared in the first two entries), Anthony Peck who played a young cop in the first and Ricky Walsh in the third film and Aldis Hodge who played Zeus' nephew Raymond in Die Hard: With a Vengeance (1995), and CIA Agent Foxy in this film (wearing military fatigues and telling Jack his window for extraction is lost).
Bruce Willis has openly stated he would like to bring back Bonnie Bedelia to the series. She originally played the character of Holly Gennaro McClane, the wife of Bruce Willis' character John McClane in the first two films of the Die Hard series, but didn't appear in the last two.
Filming of the Mi-24 Hind helicopter firing scenes took place at a military shooting range where Major Peter Simon, Air Operations Commander of Szolnok Helicopter Base, Hungarian Air Force (the pilot of the helicopter in all scenes) operated the gunship's Gryazev-Shipunov GS-30-2k (30 mm) auto-cannons and S-8 (80 mm) rockets with live ammunition to make sure the shooting effects will be as realistic as possible. Background and targets were applied in post-production.
The Cougar HEV armored truck was portrayed by four replica vehicles: three custom vehicles made by the specialists of Team Szalay, built on chassis of military surplus 6-wheeled ZIL 131 trucks, and powered by Ural truck engines. The fourth replica used for jump stunts was made in the US and was powered by a V10 Dodge Viper engine.
The black Mercedes SUV featured in a chase scene is a Mercedes-Benz G-Class. The line was developed after the Shah of Iran suggested it to the Daimler-Benz management as a possible military vehicle. The Shah was a major Daimler shareholder at the time.
Uranium-235 is a rare isotope of Uranium-238, with atoms that contain the same number of protons but fewer neutrons. "Weapons grade Uranium" is refined Uranium-235 containing less than 15% Uranium-238.
In the final action scene, the helicopter pilot says that the controls are at "full forward cyclic." This means that the cyclic stick (the joystick-like control) is pushed all the way forward in an attempt to bring the nose down.
Noam Murro was originally the director, but his commitment to the film 300: Rise of an Empire (2014) prevented him from working on this film. Other directors considered including Joe Cornish, Justin Lin and Nicolas Winding Refn.
The Mil Mi-26 transport helicopter seen at the end of the movie was rented from the Ministry of Emergency Situations of the Republic of Belarus. The original color of the helicopter is white. The temporary camouflage paint scheme was applied in Hungary, where the helicopter scenes were shot.
This was the first Die Hard film where the original script was explicitly written as an entry in the Die Hard series. The first Die Hard film in 1988 was based on a novel by Roderick Thorpe where the screenplay had originally been a possible vehicle for Arnold Schwarzenegger as a sequel to Commando. "Die Hard 2" was first written out as a script based on Walter Wager's novel '58 Minutes' with the story of a man having to save his wife when she onboard a doomed passenger flight fused into a Die Hard-based narrative. "Die Hard With A Vengeance" famously took its basic idea from Jonathan Hensleigh's screenplay Simon Says (about a man being targeted by someone he did something terrible to but then forgot existed). And "Live Free or Die Hard" was retro-fitted from the original screenplay WW3.com, which was nearly filmed on its own merits before the 9/11 terrorist attacks led 20th Century Fox to put a hold on the project while they figured out how and when a film about terrorism in the U.S. could be viable, if ever.
The 6-wheeled Force Protection Cougar HEV truck used in the street chase and car destruction scenes was driven by Zolee Ganxsta (real name: Zoltán Zana), a well-known Hungarian rapper and drummer, also famous for his extensive tattoos, playing a Russian gangster.