October was the first full month in at least 18 years in which the United States did not admit any refugees.

On Tuesday, the State Department notified refugee resettlement agencies for the third time last month that all flights for refugees who have been approved to travel to the U.S. would be postponed. The delays have ground the resettlement program to a halt, leaving hundreds of refugees, including unaccompanied children who already completed a lengthy vetting process, in limbo in some of the world’s most dangerous locations.

Refugee arrivals are typically put on hold during the first week of October while the various federal, international and nongovernmental components of the refugee system adjust to implementing a new plan for U.S. admissions, which is set by the president each fiscal year through an official determination, which is usually signed sometime before the end of September.

“We’ve never seen a moratorium last this long,” said Krish O’Mara Vignarajah, president and CEO of Lutheran Immigrant Refugee Services, one of the country’s largest refugee resettlement agencies.

“By law, no refugees may be admitted in any given fiscal year until the President signs and issues the Presidential Determination on Refugee Admissions,” a State Department spokesperson said in a statement to Yahoo News earlier this week, confirming the latest extension of the ongoing moratorium on refugee arrivals. “We have now extended it through November 5.”

As of Nov. 1, President Trump has yet to sign the Presidential Determination on Refugee Admissions for Fiscal Year 2020.

According to State Department data on monthly refugee arrivals, which is not available before fiscal year 2001, October 2019 is the first month in which zero refugees were admitted to the United States. Previously, the lowest months for arrivals had been October and November of 2001, in the immediate aftermath of the September 11 terror attacks, during which the U.S. received just four refugees each. Even then, the U.S. continued to receive at least a few refugees each month.

The State Department said it will work with agencies like LIRS “to plan for a resumption of refugee arrivals, including rescheduling travel for those affected by the extension.” However, Vignarajah emphasized that rescheduling travel for refugees is not as simple as booking a new flight.