Most likely a satellite. They look exactly like stars, but they glide across the sky smoothly.
Airplanes may have multiple light sources, some blinking lights, and you can definitely perceive how low it seems to be: An airplane somewhat seems to come from the horizon and disappear the same way, while a satellite "seems to always be at the same distance from you", like gliding on an imaginary half-sphere or dome of a night sky covering you.
Last summer I went for a night bike ride for 6 hours and during this time, I spotted 12 satellites just by observing. They're a very common thing. This time I got very lucky though, because one of the 12 satellites unexpectedly was something called an Iridium flare and I had never seen one of those in real life before.
There's a lot of man-made space junk orbiting the Earth, some satellites still operated, some not. There's a bunch of satellites known as Iridium, which happen to have a design that includes large, reflective solar panels.
I live in the North so in the summer, the sun only barely goes below the horizon and the summer nights are short. When I'm just in the dark side but an Iridium satellite happens to fly approximately above me, if everything is in a specific angle, the sun from behind the horizon hits the satellite's solar panels, and like a mirror, reflects those rays to the dark side, into a viewer's eyes.
It was my first time seeing that and I must say, it's extremely impressive when you're merely looking at a "moving star", then unexpectedly it grows very bright, brighter than any star in the night sky, and finally reverts back to the normal looking gliding satellite.
Because people are very much aware of all of the space junk that's up there, there are plenty of websites and mobile apps that you can use to see where the most common satellites are at the moment, and, because we know the route of each satellite, as well as the year and location specific data regarding the Earth and the Sun, Iridium flares can also be predicted, like you would predict things like Solar eclipses.