Introduction

The question of whether or not time travel is a real concept in the Alien, Predator, Alien vs. Predator, and Prometheus universe has long been debated in the fanbase, but now is about time to properly explore this issue and put it to bed permanently.

Evidence #1: Ripley battles Aliens, Predators, and time-travelling Terminators

In the 2000 crossover comic book Aliens Versus Predator Versus The Terminator, the time travel aspect in this fictional universe or multiverse is confirmed for the first time where the Terminator franchise connects to the continuity of Alien Resurrection and thereby provides implications for time travel to the rest of the Alien, Predator, Alien vs. Predator, and Prometheus universe.

Evidence #2: AVPR confirms time-travelling dinosaur hunters

The 2007 film Aliens vs. Predator: Requiem featured a Triceratops skull in the trophy room on a Yautja spacecraft, and considering Yautjas apparently did not evolve until thousands of years ago, thanks to the advanced Amengi species becoming involved in their evolution, while Triceratops was supposedly alive millions of years ago, it seems safe to say that (unless there is something to Yautja evolution and history we are not made aware of yet) this Yautja clan are time-travelling dinosaur hunters.

Evidence #3: Engineer time-travelling in Life and Death

During the climax of the 2017 comic book crossover Prometheus: Life and Death - Final Conflict, capping the Life and Death saga, one of the main characters, Singer, aboard the Engineer spacecraft after reaching an undisclosed destination (quite reminiscent of Planet 4 from the 2017 film Alien: Covenant) states that "we could be anywhere and anywhen", clearly hinting at the spacecraft being capable of time travel.

Evidence #4: The Predator confirms time travel is possible

The 2018 film The Predator further confirmed time travel to be a reality in that the Fugitive Predator is shown at the start of the film to be opening a portal and travelling through spacetime to reach Earth and escape the Assassin Predator which later also travels through a spacetime portal. This time travel aspect of the film was to be even further affirmed by the existence of two alternate endings featuring Lieutenant Ellen Ripley from the 1979 film Alien and Rebecca "Newt" Jorden from the 1986 film Aliens, both characters which wouldn't come to exist until more than a century later from the time when the main events of The Predator takes place (noting that the film's introductory scenes could take place at any time period).

Evidence #5: The lost tribe of Predator 2 explores space and time

NECA's recent 2020 release of a new version of the "Ultimate Armored Lost Predator", celebrating the 30th anniversary of Predator 2, features a description seemingly further confirming the time-travelling aspect of Yautja technology (noting that this same description had been used years earlier as well);

"Armored Lost Predator - a master of weapons, this mysterious mercenary of the Rogue Space Tribe was originally part of Greyback's old crew, the Lost Tribe, from which he took his name. After being tricked into a heist job with Spiked Tail and Lasershot on Yautja Prime, Lost was convicted as an accomplice to the theft of experimental Yautja technology, which included weapons and a spaceship. Being pursued by the high council and their Enforcers, the trio used the stolen prototype ship to narrowly escape off-world. After his deception, Lost had no trust for his two new partners but conceded that it's the only tribe he can still hunt with and maintain his honor. Now with an advanced ship, they can travel through space and time to explore new systems unlike any other Yautja ever could. In addition to taking mercenary jobs from other alien races, they eventually became specialised in artificial intelligence hunts, expanding well past biological targets. Silent and tactical, Lost prefers solitude and brings much-needed order to the otherwise chaotic nature of his new crew."

Conclusion

The unavoidable conclusion from these facts is that time travel is definitely a relevant aspect to the Alien, Predator, Alien vs. Predator, and Prometheus universe.