It is currently peak season at the UFO hotline in the Netherlands. Reports of UFOs increase every year when the weather warms up and skies clear in the country.

"The days are long, people are outside a lot and then you always see a peak in the number of UFO sightings", Alex Griffioen, the manager of the hotline, said to NOS. "For the vast majority of these reports there is a very simple explanation, but for 1 in 100 there's really something crazy going on." 

A video posted online showing a white light slowly pulling over Ouderkerk, turned out to be a plane, for example. Some others are harder to explain. Such as a video filmed above Arnhem that shows three flying objects. They seem to be balloons, gradually disappearing into the sky, until one suddenly makes a sharp turn and shoots left.

Since the hotline was established in 2011, over 5 thousand UFO sightings were reported. That comes down to about 70 per month. Most of the reports involve strange lights, like white or colored spheres, spots and stripes. Sometimes it involves an object moving in an unusual way. The sightings are all discussed on a forum.

"It's a pity that this subject is always placed in the fantasy corner, along with crop circles and chemtrials and such. We're just trying to look at it seriously. It's a phenomenon observed by pilots and other very reliable, sensible people", Griffioen said to NOS. 

He also has some tips for anyone spotting a UFO in the future. "It's useful to download two aps that answer a lot of questions: Skywalk lets you see the position of stars and planets. Flightradar shows the planes that come over." Try to take a clear picture. And if you record a video, make sure you have a fixed reference point in the frame.