Sharp-eyed Londoners looking up the last few nights may have noticed what looks like a bright line moving across the sky.

Spoiler alert: it's not a surveillance drone, a spy balloon, or an American fighter jet looking to shoot down unidentified flying objects entering North American air space.

It's the Starlink satellite constellation, and many are seeing it for the first time over London this week. The satellites provide Internet to remote communities in 48 countries.

"I was walking in behind Platts Lane, and I looked up and saw a whole bunch of lights in the sky, all kind of one after another," said Mac Ross. "With everything that's been going on with the balloons being shot down, I immediately was kind of concerned about what I was seeing because I'd never seen the Starlink in person."

"I hustled home and asked some friends about it, and they said, 'Oh, no, that's the Starlink," Ross said.

Starlink satellite internet is operated by Elon Musk's spacecraft and rocket launch company, SpaceX. Made up of hundreds of low-orbit satellites, they form a mesh-like network around the Earth. That network communicates with coffee table-sized satellite dishes customers can install on their roofs, bringing high-speed internet to remote users.

Exactly when and where to see the satellites can be found at findstarlink.com, said Charmi Bhatt, an astronomy PhD student at Western University and outreach worker with the Institute for Earth and Space Exploration.

"What we're seeing is actually a bunch of satellites that were launched last year, in September. They look like one bright, thin line moving through the night sky, but since they're all in a row, they end up looking like a bright line," Bhatt said.

"SpaceX hopes to have as many as 42,000 satellites in this so-called mega constellation."

As more people look up into the sky because of world events — from a Chinese balloon shot down over the United States or an unidentified flying object shot down over Lake Huron — they'll be seeing satellite trains on clear nights, Bhatt said.

"More and more people are looking into the sky now because of all these interesting objects, and it's very easy to misinterpret those as UFOs," she said.

"People should look up into the night sky for two reasons: first, it's beautiful, and you kind of make a connection with the universe, and you become more aware about your location in the universe.

"Second, to understand the new era of space technology like Starlink and the balloons. The more people will look into the sky, the more they will learn about it, and I think that's helpful to be more aware of what's going on in our near atmosphere, the Earth, but also in the universe."