Darkness. That is the common denominator for the current cases, according to Engström.
It is extremely difficult as an observer to make a good distance assessment, what am I seeing at all, how far away is this object and how big is it. It makes a difference if it happens during the day, he says.
When the police make their assessment, they compare technical data such as radar images and photos.
"Mass psychological effect"
During one week in January 2022, the police received around 200 observations of suspected drone sightings, several of which were near Swedish power plants. The majority of them were dismissed.
It's always like this, there's some kind of mass psychological effect, you start looking, "what's that?", you look up at the sky when you wouldn't normally do it and then you discover that there are lots of things moving, says Engström, also reminding of the alleged submarine sightings in the 1980s.
There's a lot of reporting around the subject, and that's why more reports come in, he continues.
Results before the end of the week
Often, there can be natural causes behind the observations, according to Engström. When it comes to suspected drone sightings in the dark, they can often be mixed up with, for example, airplanes, helicopters, satellites, and masts.
The police investigation into the current observations at Arlanda is still ongoing.
In some cases, we can say that it's not about drones, but we're not finished with all the interviews and reported incidents. But we should be able to come up with some kind of result before the week is over.
Furthermore, he says that the police will support Arlanda with equipment in the coming days to directly assess suspected observations.