The police had alerted all the airports in Germany about a possible threat

All German airports to strengthen security measures. The police took this step after in Stuttgart were seen suspicious persons who watched the work of the airport.

German police recommended all 14 airports in the country to strengthen security measures, Bild reports, citing the Federal police office in Potsdam.
According to Bild, the surveillance cameras caught unknown people watching the work of the airport in Stuttgart. Several people “were systematically following” the airport buildings and adjacent territories and behaved in a “conspiratorial”, reported by the newspaper.

“We have information, the analysis of which is not yet completed. But we have established attempts to monitor the airport of Stuttgart”, – told to newspaper the representative of the Federal police of Stuttgart Roman Stromayer. According to the DPA Agency, the warning may be related to the threat of terrorism, as one of the suspects is associated with Islamists and is considered as a potentially dangerous criminal.

Since then, the Federal police have strengthened security measures at the airport, as well as increased the number of employees in the immediate vicinity.
The representative of the Federal police confirmed to Reuters that the German airports received a warning and massively increased security measures because of the incident in Stuttgart, but to confirm or deny media reports about the identities of the suspects refused.

On the night of December 20, London Gatwick airport temporarily suspended all flights after reports of two drones seen on its territory, which is why 115 thousand people could not fly from London. ​ Gatwick-the second busiest airport in the UK, it is second only to Heathrow, also located in London. Later, law enforcement agencies reported that the invasion of drones on the territory of the airports was deliberate.