Poland will send four Soviet-era Mig fighter jets to Ukraine – becoming the first Nato country to send planes since Russia invaded last year.
Polish President Andrzej Duda said they would be sent in the coming days, with others handed over in the future.
Though a welcome boost to Ukraine’s air defence, the extra jets are not expected to be decisive in the war.
The deputy speaker of Ukraine’s parliament Olena Kondratyuk said she hoped more countries would follow.
Other Nato countries are considering sending the Soviet-era planes, which Ukrainian pilots are trained to fly.
Ukraine has previously asked Western countries for modern fighter jets, such as F-16.
The UK is training Ukrainian pilots on Nato-standard aircraft. But because of the long training times, it has warned that supplying Western jets would only ever be a long-term option.
President Biden has previously ruled out sending jets from the US to Ukraine.
At the start of Russia’s full-scale invasion, Ukraine was believed to have around 120 combat capable aircraft – mainly ageing Mig-29s and Su-27s.
President Duda said Poland still had around a dozen Soviet-era Mig 29 aircraft in operation.
Ukrainian MP Kira Rudik told the BBC: “We need them to strengthen our air defence systems and to help our army in the spring counter-offensive.
“It’s also a good sign to everybody that getting fighter jets to Ukraine is not something unspeakable or surreal – that this is something that can happen; that the only thing that is needed to make it happen is political will.”
Yuriy Sak, an adviser to the Ukrainian defence minister, told the BBC the Polish jets would be used “very efficiently by our air force”.
He said in the past 24 hours, the existing Ukrainian air force had carried out 16 air strikes on Russian personnel and equipment. But he stressed that Ukraine wanted “fourth generation” jets, such as F-16s.
“They are more universal platforms, they are more capable and of course they will make Ukrainian air forces more efficient,” he said.
Poland is a strong ally of Ukraine one of the largest suppliers of military equipment. It is currently replacing its old Soviet-era planes with newer American and Korean models.