Trivia: When Weyland is in his office near the beginning of the movie, he's playing with his pen. He starts tapping it on his desk between his fingers, alternating which two fingers he taps between. This is what Bishop does in Aliens (albeit with a knife) with his hand on top of Hudson's; maybe it was programmed into Bishop's intelligence.
Trivia: There is a dipping bird in the background of the receiving station in Nebraska just like the one in the first Alien movie. Also, the morse code in the background says, "whoever wins. we lose."
Continuity mistake: When the man is pinned to the wall by the Predator's spear there is a close-up shot of his feet showing a box beside his right foot. When it cuts to a shot from the side of the man the box is gone. (00:31:35)
Trivia: During production, the tagline "Their war. Our world." was suggested. It was ultimately passed on for "Whoever wins... we lose." However, the original tagline was subsequently recycled and used for the 2007 film "Transformers."
Trivia: The image/symbol of the Xenomorph on the floor of the sacrificial chamber is the same or similar to the symbol used in the marketing of Alien 3 and seen on the movie's cover and posters. This same symbol is also on the necklaces of the people being sacrificed, seen both in the flashbacks of them lying down, and sometimes visible on the decayed corpses in the modern time of the movie. (00:35:37)
Trivia: The helicopter approaches an ice breaker ship called the Piper Maru. This is named after the X-Files episode of the same name, which also had an ice breaker ship called the Piper Maru, which in that show was named after Gillian Anderson's daughter. Coincidentally, Lance Henriksen, who is a main character in this movie, also appeared in X-Files and got his own spin-off show as well, Millennium. (00:06:42)
Trivia: The camera lens and style at the start of the film is a clear reference to Hal 9000 from the film 2001: A Space Odyssey in how it's shaped and looks, as well as the framing and blocking with the film camera. (00:01:33)
Answer: When they emerged from the underground pyramid unscathed, the Predators assumed they were not infected. Any Predator, young or old, would have been taught to self destruct rather than be caught or killed. As seen in the previous movies. Lex was given the mark of a warrior, they assumed she was taught their code of honor.