American troops pulled out of their main military base in Afghanistan on Friday, leaving behind a piece of the World Trade Center they buried 20 years ago in a country that the top U.S. commander has warned may descend into civil war without them.

“All American soldiers and members of NATO forces have left the Bagram air base,” said a senior U.S. security official on condition of anonymity.

U.S. President Joe Biden, speaking to reporters at the White House, said that the U.S. withdrawal is “on track,” but that some American forces still will be in Afghanistan in September as part of a “rational drawdown with allies.”

Even so, the Bagram pullout brings an effective end to the longest war in American history.

The base, an hour’s drive north of Kabul, was where the U.S. military has coordinated its air war and logistical support for its entire Afghan mission. The Taliban thanked them for leaving.

“We consider this withdrawal a positive step. Afghans can get closer to stability and peace with the full withdrawal of foreign forces,” Taliban spokesman Zabihullah Mujahid told Reuters.

Other Afghans were more circumspect. “The Americans must leave Afghanistan and there should be peace in this country,” said Kabul resident Javed Arman. But he added: “We are in a difficult situation. Most people have fled their districts and some districts have fallen. Seven districts in Paktia province have fallen and are now under Taliban control.”

For the international forces, more than 3,500 of whom died in Afghanistan, the exit came with no pageantry. A Western diplomat in Kabul said the United States and its NATO allies had “won many battles, but have lost the Afghan war”.

It was at Bagram, by a bullet-ridden Soviet-built air strip on a plain hemmed in by the snow-capped peaks of the Hindu Kush, that New York City firefighters and police were flown to bury a piece of the World Trade Center in December, 2001, days after the Taliban were toppled for harbouring Osama bin Laden.

It was also here that the CIA ran a “black site” detention centre for terrorism suspects and subjected them to abuse that President Barack Obama subsequently acknowledged as torture.

Later it swelled into a sprawling fortified city for a huge international military force, with fast food joints, gyms and a cafe serving something called “the mother of all coffees”. Two runways perpetually roared. Presidents flew in and gave speeches; celebrities came and told jokes.

An Afghan official said the base would be officially handed over to the government at a ceremony on Saturday.

The U.S. defence official said General Austin Miller, the top U.S.commander in Afghanistan “still retains all the capabilities and authorities to protect the force” stationed in the capital, Kabul.

Earlier this week, Miller told journalists in Kabul that civil war for Afghanistan was “certainly a path that can be visualised”, with Taliban fighters sweeping into districts around the country in recent weeks as foreign troops flew home.

Two other U.S. security officials said this week the majority of U.S. military personnel would most likely be gone by July 4, with a residual force remaining to protect the embassy.

That would be more than two months ahead of the timetable set by Biden, who had promised they would be home by Sept. 11, the 20th anniversary of the attack that brought them here.

Washington agreed to withdraw in a deal negotiated last year with the Taliban under Biden’s predecessor Donald Trump, and Biden rejected advice from generals to hang on until a political agreement could be reached between the insurgents and the U.S.-backed Kabul government of President Ashraf Ghani.

A Boeing 737 cargo aircraft with two crew on board was forced to make an emergency landing on the water off Honolulu early Friday after the pilots reported engine trouble.

Transair Flight 810 had been expected to go from Honolulu to Kahului, the main airport on Maui, according to aviation data from FlightAware.

The plane was “attempting to return to Honolulu when they were forced to land the aircraft in the water” at about 1:30 am local time, an FAA spokeswoman said in a statement.

“According to preliminary information, the US Coast Guard rescued both crew members. The FAA and National Transportation Safety Board will investigate,” the statement said.

A spokesman for the Coast Guard, Petty Officer Third Class Matthew West, said a Coast Guard helicopter rescued one of the crew, while “a fire department helicopter rescued the other.”

A Coast Guard cutter was also dispatched to the scene.

Both crew members were taken to a Honolulu hospital for treatment, West said, adding he did not have additional information about their condition.

A source with knowledge of the incident said the plane appears to be a 737 Classic that was likely at least 33 years old.

A Boeing spokeswoman said the company is “aware of the reports out of Honolulu” and “closely monitoring the situation.”

The aviation giant said it was in contact with the NTSB, which investigates civil air accidents, and was “working to gather more information.”

Both the FAA and the NTSB will probe the incident. Landings on water are rare.

In January 2009, an Airbus A320 passenger jet made an emergency landing on the Hudson River in New York shortly after takeoff, after flying into a flock of geese, severely damaging both engines.

The pilot, Chesley “Sully” Sullenberger, believed he could not make it back to LaGuardia Airport and landed the plane in the river, with 150 passengers and five crew on board. No one was killed in the incident.

Boeing’s safety record was called into question after the fatal crashes of two 737 MAX passenger planes in 2018 and 2019, leaving nearly 350 people dead. The plane was grounded for 20 months after the crashes.

Investigators said a main cause of both crashes was a faulty flight handling system known as the Maneuvering Characteristics Augmentation System, or MCAS.

Boeing shares dipped slightly Friday after the announcement of the Hawaii incident.