In the cave of bats scene, the 'bats' seen on screen were actually added after filming as a special effect. Real bats were brought in to fill the cave, but Sylvester Stallone and Janine Turner were too afraid to shoot the scene with live bats.
The movie is in the Guinness Book of World Records for the costliest aerial stunt ever performed. The scene in which Travers crosses from one jet to the other at a height of 15,000 feet was done without the aid of any safety devices or trick photography. The insurance company underwriting the film refused to insure a stunt man for this, so Sylvester Stallone offered to reduce his own fee for the movie by the amount that the stunt cost to produce in order that the film could be made. The stunt was performed by Simon Crane. Because of the extremely dangerous nature of the stunt, it was only performed once.
In the opening scene where Sarah slips from Gabe's hand had to be done several times because Sarah's glove would not slip off as desired. In order to get it to slide off, director Renny Harlin had her wear a glove that was a couple of sizes too big and filled the glove with Vaseline and even then Sylvester Stallone's grip was too tight and the glove almost stayed on.
Sneak-preview audiences saw a scene where a rabbit gets killed by gunfire. Their reaction was strong enough for Sylvester Stallone to invest $100,000 of his own money to have the scene re-shot so that the rabbit escaped.
Set in Colorado, but filmed in the Cortina d'Ampezzo-Dolomites mountains, because of their spectacular similarities to the Colorado Rockies. The production paid 80.000.000 Lire to enter all mountain areas.
Carolco had originally signed Sylvester Stallone to appear opposite John Candy in a comedy directed by John Hughes about feuding neighbors. When the project was dropped, Stallone was persuaded to appear in Cliffhanger.
Cliffhanger is in the Guinness Book of World Records for the costliest aerial stunt ever performed. Stuntman Simon Crane was paid $1 million to perform the aerial transfer scene, where he crossed between two planes at an altitude of 4,572 m (15,000 ft).
Electrical storms hit during filming, knocking down five crew members. Climber Earl Wiggins was hit three times, but was only slightly injured. During a later storm, crew members had fun taking pictures of each other with their hair standing on end while the climbers pointed out the wisdom of evacuating.
The two-story high cliff built for the climactic battle sequence burned to the ground completely in eight minutes when the miniature helicopter explosion got out of control. The heat of the fire was so intense it melted one of the cameras.
Ron Kauk was Sylvester Stallone's stunt double and really had to bulk up. He ate 5 carbohydrate-heavy meals a day and pumped a lot of iron. The trainer wanted to have him eat a sixth meal in the middle of the night. Kauk also doubled for Leon, a 6'3" black actor, and Janine Turner.
The stuffed puppy that falls off the cliff in the opening scene was not scripted but was added at the last minute. Renny Harlin liked the dog so much he bought it so that the audience would have a clear idea of what would happen and how horrific the fall was.
The movie's most breathtaking scenes were shot in the Cortina d'Ampezzo Dolomites mountains. The bridge scene was shot on Monte Cristallo - ferrata Ivano Dibona. The crew stayed in Cortina more than 3 months. Further filming took place in Durango, Colorado. The credits of the film also thank the Ute Tribe for filming in the Ute Mountain reservation.
In the original cut of the film shown to test audiences, there was a 40-foot jump from one cliff to another that Sylvester Stallone's character performs. This scene appears in the theatrical trailers to the film. It was cut because test audiences laughed out loud when they saw it and thought it was totally impossible. The clip of the jump was redone and used for a shorter jump off a cliff near the end of the film using computer graphics and special effects.
Carolco had originally signed Renny Harlin to direct Gale Force (1999), a "Die Hard-in-a-Hurricane" action movie. The special effects proved too difficult at the time, so he was persuaded to direct Cliffhanger.
An avid golfer, Sylvester Stallone found that climbing roughed up his hands and consequently messed up his game. He had a net on the set for practice. The models he was dating complained about his rough hands.
After Michael France sold the "Cliffhanger" script to Carolco Pictures for $500,000, the company was visited by two independent producers, Gene Hines and James Zatolokin, who provided proof that France was not the originator of the story. It turned out the idea had been first developed in the 1980s by Hines and a world-famous climber and author John Long. Carolco agreed to pay Hines and Zatolokin a producers' fee of $400,000 and gave them co-producing credit. John Long received a "Based on a premise by..." credit.
Was originally titled "Gale Force" under the Carolco studio. The script concerned Sylvester Stallone fighting a band of terrorists/thieves in a coastal town during a hurricane. Deemed too expensive to produce (after investing roughly $2 million in script rewrites and the original), the plug was pulled. The basic concept was then carried over to this film with the same director (Renny Harlin) and star (Sylvester Stallone) attached.