• The aircraft went down amid a barrage of Russian missiles on Monday, killing pilot Oleksiy Mes, Ukraine's military said.
• The cause of the crash was not a direct result of an enemy missile strike, the Ukrainian military claims.
One of the F-16 fighter jets sent from Nato allies to Ukraine has been destroyed, a Ukrainian military source has told the BBC.
The aircraft went down amid a barrage of Russian missiles on Monday, killing pilot Oleksiy Mes, Ukraine's military said. It marks the first loss of its kind since the planes were delivered earlier this month.
The cause of the crash was not a direct result of an enemy missile strike, the Ukrainian military claims.
It said the pilot destroyed three cruise missiles and one drone in Russia's largest aerial attack to date.
"Oleksiy saved Ukrainians from deadly Russian missiles," the Ukrainian Air Force wrote in a statement on social media.
"Unfortunately, at the cost of his own life."
The statement did not specify the type of plane involved, but a military source told the BBC the pilot was flying an F-16.
Ukrainian President Volodymyr Zelensky officially confirmed on Tuesday the US-made F-16's were being deployed to shoot down Russian drones and missiles.
This week, he asked allies to allow Ukraine to use long range missiles to hit targets further into Russia.
Dutch Chief of Defence Gen Onno Eichelsheim confirmed the Netherlands will provide Ukraine with 24 of the jets, in addition to more weapons.
There will be no restrictions on their usage apart from complying with humanitarian law, he told a conference in Washington on Wednesday - meaning Kyiv could launch deeper strikes into Russian territory.
Around 65 F-16s have been pledged by Nato countries since US President Joe Biden first authorised willing European allies to send them to Ukraine in August 2023.
Ukraine's F-16s work alongside a limited number of Western-supplied surface-to-air missile systems such as Patriot and Nasams which are already on the ground.
They also help defend against Russian glide bombs - dumb munitions fitted with pop-out wing kits and guidance modules to deliver precision strike stand-off capabilities, similar to the JDAM munitions from the United States.
The destruction of the aircraft is blow to Zelensky, who said he will deliver a "victory plan" to US President Joe Biden next month.
He also revealed Ukraine had recently carried out the first successful test of a domestically-produced ballistic missile, but declined to share any more details.