The US has approved the transfer to Ukraine of American-made F-16 fighter jets from Denmark and the Netherlands when Ukrainian pilots are fully trained to operate them.
"This way, Ukraine can take full advantage of its new capabilities," a US state department spokesman said.
Ukraine praised the decision it had been pushing hard for since last year.
But it is expected to be months before Kyiv will be able to use F-16s to try to counter Russia's air superiority.
The Dutch are thought to have about 24 operational F-16s which are scheduled to be taken out of service and replaced by more advanced war planes.
Denmark is also planning an upgrade of its fleet of some 30 F-16s.
The US and its allies had earlier ruled out providing F-16s to Ukraine, fearing that this would lead to further escalation with a nuclear-armed Russia.
Russia - which launched a full-scale invasion of Ukraine in February 2022 - has so far made no public comment on the issue.