We suspect that it was a deliberate act, but I cannot answer what the purpose was. Due to the secrecy of the preliminary investigation, we do not want to go into what type of drone was sighted or by whom, says police spokesperson Daniel Wikdahl to SVT News.
It is said to have been about four drones of varying sizes, according to Cecilia Bengtström, on-call officer at the Swedish Transport Agency's press service.
Redirected
About five planes had to be redirected to Nyköping and Gothenburg respectively due to the stop, according to Swedavia's press service for TT. Redirects were also made to airports in Finland and to Copenhagen, according to Expressen and Aftonbladet.
One of the planes that landed at Skavsta outside Nyköping had declared an emergency and was met by fire trucks, reports Aftonbladet.
It's more undramatic than it sounds. The plane had low fuel levels and that happens on routine. The landing went well, says Jörgen Hansson at the air rescue center to the newspaper.
The drones were sighted just before 01 and the Swedish Transport Agency then decided to redirect all planes. At 03:30, traffic resumed at Arlanda.
The police are investigating the incident as airport sabotage and a crime against the Protection Act.
We have been in contact and collaborated with other authorities and the question is assessed as a police matter, at least for now, says Daniel Wikdahl at the police.
Suspected drones in Uppsala
At 22:00 on Sunday, the police received an alarm about suspected drones in Uppsala, reports Upsala Nya Tidning. They are said to have moved near protected objects and a report of a crime against the Protection Act has been filed.
They moved near our facilities, i.e. the police's premises, says Tobias Ahlen-Svalbro to the newspaper.
Whether there is a connection between the drones that flew near Arlanda is too early to say, according to the police.
For the crime of airport sabotage, the penalty can be up to four years in prison, if the act is intended to cause danger to the airport's function or safety. If the crime is aggravated – and there was a risk to human life – the penalty can be up to life imprisonment.