(CNN) The US Air Force has pulled 26 Turkish military personnel from its F-35 fighter jet training program due to "safety" concerns stemming from the ongoing dispute over Turkey's push to buy both American stealth aircraft and a Russian missile defense system, according to a defense official directly familiar with the matter.

Specifically, Air Force officials were concerned the pending decision to end Turkey's involvement in the F-35 program this summer if it moves forward with a plan to purchase the Russian S-400 air defense system could impact the Turkish pilots' focus, the official said.

Brigadier Gen. Todd Canterbury, the wing commander at Luke Air Force Base, made the decision on his own Friday despite there being no evidence the Turks pose a threat to the aircraft or US personnel or would be unable to concentrate on flying.

The safety concern is being explained as the same procedure used to temporarily ground US military pilots if they are facing a "significant life event," such as a divorce or death in the family, that would be a distraction during flight operations, the official told CNN.

Lt. Col. Mike Andrews, Department of Defense spokesman, confirmed the pilots are no longer training.

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