Afghanistan's aviation authority has said the country's airspace had been "released to the military" and advised airlines to avoid its air corridors, prompting major airlines to divert flights in the wake of the Taliban's takeover of Kabul.
The authority did not specify which military, given the collapse of local security forces in the face of the Taliban offensive.
But US forces have taken over air traffic control at Kabul airport, where five died on Monday in chaotic scenes with reports of firing in the air and a stampede.
United Airlines, British Airways and Virgin Atlantic had already stopped using Afghanistan airspace on Sunday as US-led forces departed and Western nations scrambled to evacuate citizens.
On Monday, Qatar Airways, Singapore Airlines, Taiwan's China Airlines, Air France KLM and Lufthansa followed suit.
Air France said six routes were affected: Bangkok, Delhi, Singapore, Mumbai, Madras and Ho Chi Minh.
Lufthansa said flight times to India and some other destinations would be extended by up to one hour, in a move that will add to fuel costs.
In a notice to pilots on its website, the Afghanistan Civil Aviation Authority (ACAA) said any transit through Kabul airspace - which covers all Afghanistan - would be uncontrolled, meaning planes would no longer be guided from the ground.
"Kabul airspace has been released to the military. Advise transit aircraft to reroute," the notice said.
"Any transit through Kabul airspace will be uncontrolled. Surrounding FIRs (air traffic control regions) have been advised."
Some flights turned around right after the announcement. Flight tracking website FlightRadar24 showed an Air India flight from Chicago to Delhi changed course and exited Afghanistan's airspace shortly after entering, while a Terra Avia flight from Baku to Delhi did the same.
The Air India flight later diverted to Sharjah in the United Arab Emirates for more fuel, FlightRadar24 said. Air India did not respond immediately to a request for comment.
Analysts said flights between Europe and parts of Asia would be among those most affected, adding to growing route headaches after Middle East conflicts and the forced diversion of a jet over Belarus, which put its skies off limits to many airlines.
A Western aviation official said the withdrawal of air traffic control services would also have implications for any airlines seeking insurance to keep flying over Afghan territory.