BERLIN (AP) – An air deployment exercise billed as the biggest in NATO’s history and hosted by Germany got underway on Monday.

The Air Defender 2023 exercise that is set to run through June 23 was long-planned but serves to showcase the alliance’s capabilities amid high tensions with Russia.

The first planes took off on Monday morning from airfields in northern Germany. Some 10,000 participants and 250 aircraft from 25 nations will respond to a simulated attack on a NATO member. The United States alone is sending 2,000 U.S. Air National Guard personnel and about 100 aircraft.

12 June 2023, Mecklenburg-Western Pomerania, Laage: At Tactical Air Squadron 73 “Steinhoff” at Rostock-Laage Airport, two Bundeswehr Eurofighters take off for the start of the air exercise “Air Defender 2023”. Until June 23, 25 nations as well as NATO are taking part in the largest air exercise since NATO came into existence, under German leadership. According to the Bundeswehr, around 10,000 soldiers and 250 aircraft are taking part. Among them are 70 aircraft from Germany. Photo: Bernd Wüstneck/dpa (Photo by Bernd Wüstneck/picture alliance via Getty Images)

12 June 2023, Lower Saxony, Wunstorf: An Airbus A400M of the German Air Force with the logo of the international air force maneuver “Air Defender 2023” is parked at Wunstorf Air Base in the Hanover region. From June 12 to 23, 25 nations and 10,000 soldiers with 250 aircraft will take part in the Air Defender 2023 maneuver under German leadership. Photo: Julian Stratenschulte/dpa (Photo by Julian Stratenschulte/picture alliance via Getty Images)

09 June 2023, Schleswig-Holstein, Jagel: An Air Force Tornado aircraft stands over Jagel Air Base during a media day for the Air Defender 2023 exercise. Preparations for the large-scale international exercise over parts of Germany have been completed. (to dpa “Preparations for air force exercise “Air Defender 2023″ completed”) Photo: Daniel Bockwoldt/dpa (Photo by Daniel Bockwoldt/picture alliance via Getty Images)

“The exercise is a signal – a signal above all to us, a signal to us, the NATO countries, but also to our population that we are in a position to react very quickly … that we would be able to defend the alliance in case of attack,” German air force chief Lt. Gen. Ingo Gerhartz told ZDF television.

Gerhartz said he proposed the exercise in 2018, reasoning that Russia’s annexation of Crimea underlined the need to be able to defend NATO.

Russia´s invasion of Ukraine in February 2022 has jolted NATO into preparing in earnest for the possibility of an attack on its territory. Sweden, which is hoping to join the alliance, and Japan are also taking part in the exercise.

Assessments of the extent to which the exercise will disrupt civilian flights have varied widely. Matthias Maas, the head of a German air traffic controllers’ union, GdF, has said that it “will of course have massive effects on the operation of civilian aviation.”

Gerhartz disputed that. He said that Germany’s air traffic control authority has worked with the air force to keep disruption “as small as possible.” He noted that the exercise is limited to three areas which won’t all be used at the same time, and that it will be over before school vacations start in any German state.

“I hope that there we will be no cancellations; there may be delays in the order of minutes here and there,” he said, insisting that a study cited by the air traffic controllers’ union assumes a worst-case scenario in bad weather in which the military wouldn’t fly anyway.