This was the latest shock to tourism in Turkey, which has taken a hit from a number of bombings this year, including a suicide attack in June that killed 45 people at Istanbul's main airport.
A Reuters witness in Istanbul, citing a pilot, said all upcoming flights from the Istanbul airport had been canceled.
Flight tracking website FlightAware.com so far listed 32 canceled departures for Friday and Saturday.
A British Airways flight to Istanbul diverted to Sofia, Bulgaria, and a Lufthansa flight to Istanbul returned to its origin in Frankfurt, company spokeswomen told Reuters.
British Airways said on its website that customers traveling through Istanbul this weekend could rebook travel.
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Some travelers reported on social media that they or their loved ones were stranded.
Twitter user Cynthia Wee (@Its_A_Cyn) said, "many stranded at airport #help," noting in another post that she was stuck in Istanbul with her family and scared.
The U.S. Federal Aviation Administration said all U.S.-inbound flights from Istanbul that were in the air prior to the airport's closing would be allowed to land in the United States as planned. Turkish Airlines and other carriers did not immediately comment.
As of July 2, international flight bookings to Istanbul for trips in the second half of the year were down 36 percent from a year ago, travel data analysis company ForwardKeys said on its website.
Arrivals from the Americas and Asia-Pacific were down 45 percent, according to ForwardKeys. In the past six months, bombings in Istanbul led to progressively sharper declines in bookings, it said.
Turkey's prime minister said the attempted coup would be put down. President Tayyip Erdogan has ruled Turkey since 2003, and Turkey is one of the most important U.S. allies in the region.
