Frum take:
1. ALIENS. If you are not an American citizen, you are an alien from an American perspective. The word means “non-citizen” (and is fairly unique to English legalese, most languages, such as Hebrew, use the word meaning “foreigner” instead).
2. UFO’s (unidentified flying objects). So the government has trouble finding a flying object bigger than commercial airliner? And it wasn’t even trying to be stealthy. If you are in the military aviation business, keeping your flying objects unidentified probably earns you a bonus.
3. Extraterrestrial Beings. None are likely to be encountered given the probability of the impossibility of faster than light transportation (and we’ve been able to observe nearby planets, finding no signed of life). If Ha-Shem wanted to tell us they don’t exist at all, it would be in Torah (at least in the oral Torah). Since there are plenty of hints in our traditions that sentient beings other than humans exist, they probably do, but who cares since it is at most a theoretical concept with no real world impact.