Aliens are not real. At least, people who claim that they have seen aliens never have any good proof to back up their claims. You should never believe something unless it can be proven, and a lot of times people who say that they saw a UFO or an alien are either trying to get attention, or saw or experienced something that they don't understand.
Also, UFO stands for Unidentified Flying Object. So, if I had never seen a football, and one came sailing through the sky toward me, I could call it a UFO. But I would not claim that it came from outer space. People do see UFOs (and some are seen from airplanes, like you asked) but they are often just an airplane, or a balloon, or something else that is natural or man-made. No UFOs that I have heard of have been seen by astronauts in space.
The most important thing when talking about aliens and UFOs is to be skeptical. The astronomer Carl Sagan came up with something called the "Baloney Detection Kit", which is a way to think about things to tell if you should believe them, or if you should say "that's a bunch of baloney!". Check out this website.
On the other hand, just because there is no good evidence that aliens are visiting us, that doesn't mean that we are alone in the universe. The problem is, if anyone out there is alive, they are an awfully long way away. Space is huge! Here's an example: if you shrank the earth down to be one inch across, the sun would be about 985 feet away, and the nearest star would be about 50,000 miles away! And that's just the nearest star! There are billions of stars out there that are millions of times farther away.
So, there could be other living things out there in the universe, but it's too far away for any of them to travel to visit us. Some scientists use radio antennas to listen to far away stars to see if someone out there is sending us radio signals. This is called the Search for Extraterrestrial Intelligence, or SETI.
To finish, I'll leave you with a quote from Carl Sagan, who was very interested in SETI:
"If it is just us [in the universe] it seems like an awful waste of space."
Origin: paranormal-factor.blogspot.com
