Die Hard 24/7 was a proposed crossover between the 24 and Die Hard franchises, but here's why it came to nothing. Die Hard was based on the novel Nothing Lasts Forever by Roderick Thorp, which saw a retired detective having to deal with the terrorist takeover of a skyscraper. The eventual movie adaptation made the character younger, with Bruce Willis' John McClane having to save his kidnapped wife inside of his daughter. Die Hard is now a classic of the action genre, and Willis returned for four sequels in the decades that followed. 24, on the other hand, launched in 2001.
The first season of 24 followed Kiefer Sutherland's Jack Bauer, a counter-terrorist agent charged with preventing the assassination of a presidential candidate. 24's real-time format, relentless pacing and Sutherland's charismatic lead turn saw 24 grow from respectable ratings success to pop culture phenomenon over the course of a few seasons. The show did receive critiques for its depiction of torture as a plot device, but it also largely received great reviews for its performances and innovative format.
Die Hard and 24 are two franchises that are currently on ice. While the fifth entry A Good Day To Die Hard was a success, it also received poor reviews from critics and fans. Sutherland exited 24 following the 2014 limited series Live Another Day (where he wanted Jack to die), while the Jack-free spinoff 24: Legacy only lasted a season. While both properties were Fox franchises with determined lead characters, they don't have much else in common. That said, a proposed crossover movie dubbed Die Hard 24/7 was once in development - until Kiefer Sutherland supposedly nixed it.
Little is known about Die Hard 24/7's storyline either, though it would have paired John McClane with Jack Bauer for a buddy cop-style thriller. It sounds like Jack would have been the straight man of the two since Bauer isn't known for making many wisecracks. Die Hard 24/7 was set to be the fifth film in the Die Hard movie series, but according to a 2010 report by AICN, Sutherland just wasn't keen on the idea. 24's original series ended with season 8 and plans were in place for a 24 movie, which spent years in development.
Sutherland reportedly wanted to focus on a solo 24 movie, and not include Jack Bauer in another franchise. While the 24 movie didn't happen, Sutherland likely made the right call. Die Hard 24/7 would have blended two series that aren't very comfortable fits together, and such a crossover would likely have been seen as a gimmick. Die Hard 24/7 stayed in place as a working title for the eventual fifth Die Hard, while the 24 film was scrapped and Sutherland returned for Live Another Day instead. There's also talk of a 24 TV show revival, but nothing has been confirmed.