Arlanda, Sweden's busiest airport, has halted flights a total of four times so far in August after drones were spotted in the airspace around the airport, and Stockholm's second airport, Bromma, three times.
Last week, planes were forced to hold or divert at Arlanda due to drones on two separate occasions. On one of those, two incoming flights were given special permission to land because they were low on fuel.
“You can't underestimate how serious the shut-down of operations on several occasions is and that aircraft have been forced to declare an emergency and use the last of their fuel to land at the closed airport,” said Tomas Gustafsson, chairman of the Swedish Pilot Association's air safety committee.
Regulations vary by country, but in Sweden if a drone is spotted in an airport's control zone it has to close for 30 minutes, or until it has been established that the drone has landed, according to directives issued by the Swedish Transport Agency, writes the pilots' union in a press statement.
Arlanda's control zone extends to large parts of northern Stockholm.
“We're approaching the limit at Arlanda when these situations can no longer be seen as unforeseen factors. That's why our recommendation is not to fly to Arlanda without enough fuel to make it to another airport if need be,” said Gustafsson, urging authorities to make the same recommendation.
Both Swedish and European air traffic authorities are investigating new rules for drones to make it possible for drones and other aircraft to use the same airspace without compromising on safety.
The Swedish Transport Agency declined to comment when approached by the TT news agency.