Unidentified Flying Objects (UFOs) are flying extraterrestrial vehicles rumored to appear in Grand Theft Auto IV.
Around the city, at almost any time throughout the day, the player can witness small blinking lights flying across the sky. These particular lights look very much like the strange lights witnessed in GTA San Andreas, but the only difference is that these lights have a little blinking strobe light above them. They also lack a vapor trail, and the player can never catch them or get close to them. The lights will always remain a set distance away from the player, therefore they will never be able to be reached. These lights can be seen at almost any time when the player looks up into the sky. These are in fact there to represent actual terrestrial aircraft.
It has been rumored that game developers added these lights to the game to look like UFOs traversing the sky. Rockstar has not explicitly made any comments about these strange lights, or about their purpose in the game. Nevertheless, it still remains a mystery why these strange lights have been included in GTA IV, because the game features real solid airplanes that regularly fly over the sky. It should be noted they differ from the distant lighting found at street level or from helicopters. When looked at closely, the lights seem to be displaced lights, which were supposed to be on planes.
Other than this evidence, most of the online photos or videos showing any other type of alien aircraft in the game are the result of mods or hacks making this myth unlikely.