Delta Air Lines announced it will suspend its seasonal service from New York's John F. Kennedy International Airport to Istanbul, which was due to restart in May.
The Atlanta-based carrier cited "increased security concerns in Turkey" including a State Department travel warning, and "weaker demand for air travel to this market."
The State Department's Turkey travel warning updated March 29 "warns U.S. citizens of increased threats from terrorist groups throughout Turkey and to avoid travel to southeastern Turkey," particularly near the Syrian border.
With Delta's announcement Wednesday, Turkish Airlines' stock declined 6.8 percent.
Meanwhile, Turkish Airlines still plans to launch service from Atlanta to Istanbul on May 16. The carrier announced last June its plans to fly the long-awaited route with Boeing 777-300ER jets.