TOKYO — Guam has been rapidly losing tourists from Japan since North Korea threatened in August to attack the U.S. Pacific territory, prompting U.S. airlines to terminate in January flights connecting the island with the country.

Given its geographical proximity, the island had been a popular tourist destination for Japanese, who accounted for roughly half the total number of tourists to Guam in 2016. Of the 1.54 million people who traveled to Guam that year, some 746,000 were Japanese, according to the Guam Visitors Bureau.

However, the trend changed drastically after Pyongyang’s Korean People’s Army said in early August it is “seriously examining” a plan to simultaneously fire four ballistic missiles over Japan for an “enveloping strike at Guam.”

The announcement sparked concerns among travelers, especially Japanese schools that had planned student trips to Guam, leading to a number of cancellations of such plans.

The number of Japanese travelers to Guam dropped 38 percent in October from a year earlier, posting a double-digit decrease for the third straight month.

The number of visitors from China and Taiwan also dived more than 40 percent each in October, dealing a blow to the island where tourism is its mainstay industry.

Following the move, Delta Air Lines Inc. announced it will terminate its flights connecting Japan’s Narita airport with Guam on Jan. 8, thus withdrawing from services carrying passengers from Japan to the island. United Airlines Inc. also plans to stop its flights between Sapporo in northern Japan and Guam on Jan. 15.

Meanwhile, Japan Airlines Co. is set to increase the number of flights between Narita and Guam from March 25 to Oct. 27 despite seeing its capacity utilization rate for the route tumble 20 percent year on year in October.

“We decided to increase the number of flights after taking into account profitability and calls among people in Guam that Delta’s withdrawal will severely affect the local tourism industry,” said a senior JAL official.