Spokesman Sean Robertson told Anadolu Agency that two generals, one from each country, flew on the same helicopter on Saturday.

This “milestone” followed establishment of the joint coordination center earlier this week, Robertson said in an emailed statement.

This flight demonstrates U.S.’s commitment to address “Turkey's legitimate security concerns on their southern border”, the statement underlined.

The statement also reiterated U.S.’s determination to “maintain security in northeast Syria so IS cannot reemerge”.

The first joint helicopter flight between the two NATO allies allows the coalition and U.S.’s partners to “remain focused on achieving the enduring defeat of ISIS,” the statement added.

In a phone call Wednesday, Turkish Defense Minister Hulusi Akar and U.S. Defense Secretary Mark Esper agreed to launch the first phase of the Syria safe zone plan as of Aug. 21.

Akar said a safe zone east of the Euphrates River in Syria should be established within the framework of the principles set out in the calendar without delay, the Turkish Defense Ministry said in a statement.

Akar and Esper also agreed that military delegations from the two countries will meet in Ankara soon to discuss the next stages of the safe zone plan, it said.

Turkish and U.S. military officials reached an agreement on Aug. 7 that the safe zone in northern Syria will serve as a "peace corridor" for displaced Syrians longing to return home and a Joint Operations Center in Turkey will be set up to coordinate its establishment.

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