A plane carrying British Defense Secretary Grant Shapps experienced GPS signal interference as it flew near the Russian enclave of Kaliningrad on Wednesday, but the plane’s safety was not compromised, Downing Street said Thursday, according to AFP.

Returning on Wednesday from Poland, where he was taking part in training as part of a major NATO exercise, “the aircraft carrying the defense minister and his delegation experienced temporary GPS jamming while passing near Kaliningrad,” the prime minister’s spokesman said Rishi Sunak.

The source added that the security of the plane was not compromised. It is not “unusual” for planes to experience GPS jamming near the Russian enclave, the spokesman added.

According to The Times, whose journalists were on board the plane, the phenomenon lasted half an hour. Phones could no longer connect to the Internet, and the plane had to use alternative methods to determine its location.

Britain has been one of Ukraine’s biggest supporters since Russia invaded it two years ago.

The Steadfast exercise is NATO’s largest exercise since the end of the Cold War. About 90,000 troops were mobilized within weeks, along with dozens of ships, armored vehicles and fighter jets.

The main purpose of the drills is to test the alliance’s ability to quickly mobilize and transport US troops to “strengthen the defense of Europe,” according to NATO, which the Kremlin described as a “threat” soon after the drills began.