Ukraine's military has released several videos showing Russian helicopters being shot down by surface-to-air missiles.
One, from last week, shows a Russian helicopter flying low, just above the tree line - in the hope of avoiding what's about to happen next. Tracking its path is the smoking trail of a surface-to-air missile. In a matter of seconds the missile has found its target. On impact the Russian helicopter crashes to the ground, before bursting into a fireball
Russian aircraft are being shot down by Ukrainian forces - as well as the video above, this video shows a jet hit near Kharkiv - and military analysts believe there's evidence that recently supplied weapons by the West are already being used.
Justin Bronk, a research fellow on airpower at the Royal United Services Institute, says there's been visual confirmation of at least 20 Russian aircraft shot down in Ukraine so far - both helicopters and jets. That's significantly fewer than claimed by Ukraine's ministry of defence, which says it has downed 48 Russian planes and 80 helicopters. Yet even the lower number shows Russia's struggled to gain supremacy in the skies.
Ukraine has suffered losses too. But UK Defence Secretary Ben Wallace told the BBC that Russia had so far not been successful in destroying the country's air defences and air force.
Before the war began, Ukraine's military aircraft were outnumbered at least three-to-one by those that had been amassed on the border by Russia.
Mr Wallace said Ukraine's ability to keep some of its air defences intact was already forcing Russian aircraft to fly at night to avoid detection.
Shoulder-launched air defence missiles, also known as Manpads (man-portable air defence systems) are just one of the weapons that Western nations have been supplying to Ukraine. They include the infamous US-made Stinger surface-to-air missiles - scourge of Soviet aircraft during its occupation of Afghanistan in the 1980s.
Exact numbers are hard to come by. Last week Mr Wallace told the BBC the West had now delivered "thousands" of anti-tank weapons and "over a thousand" Stingers. CNN, quoting a US defence official, put the total at 17,000 anti-tank weapons and 2,000 Stingers, sent by the US and Nato allies.
Britain and America had provided weapons to Ukraine before the invasion began on 24 February, with the UK delivering 2,000 light anti-tank missiles (Nlaws). Commenting on reports that they were already being used to destroy Russian armoured columns, Mr Wallace said "we've got anecdotal evidence to verify that".
Rifles and ammunition
Most countries, though, only started to send weapons in response to the Russian invasion. In all, 14 nations have supplied arms. They include Sweden and Finland, both of which have a long history of neutrality and are not members of Nato. But both have sent thousands of anti-tank weapons to Ukraine.
Germany has supplied 1,000 anti-tank weapons and 500 Stinger missiles. The Baltic states have also delivered thousands of weapons including Stingers and Javelin missiles, one of the world's most effective anti-tank weapons with a range of 2.5km (1.5 miles). Ukraine says it has already successfully destroyed several Russian T-72 tanks.
Recent weapons deliveries also include tens of thousands of assault rifles and machine guns, anti-tank mines and hundreds of tonnes of ammunition, as well as body armour and helmets, and medical supplies.
How are the weapons getting through?
The UK says it is helping "facilitate" the deliveries of these weapons. Western officials, though, are not giving details of how the supplies are getting through.
But it's no secret that while Russia's military operations have been focused in eastern Ukraine, the flow of people and supplies from the west of the country has continued via neighbouring European states. The BBC has spoken to the defence ministries of Estonia, Sweden and Denmark, all of whom confirmed their weapons supplies had been tracked and successfully reached Ukraine in recent weeks.
So, how much difference are these weapons consignments making?
Weapons supplied by the West can make a difference, but only if Ukraine continues to have armed forces capable of using them.
Mr Bronk says Ukraine's ability to retain some of its older, Soviet-era, air defence systems - which have a longer range - has forced Russian aircraft to fly lower. But that makes them more vulnerable to the shorter-range surface-to-air missiles being supplied by the West.
Without those longer-range air defence systems, Russian aircraft could fly higher to avoid the dangers of shorter-range air defences.
Meanwhile, America and European allies are looking to increase their arms supplies to Ukraine. There may be a limited opportunity before Russia tries to target any supply lines of weapons.
The US Secretary of State, Antony Blinken, has said he's had talks with Poland about it supplying Russian-made Mig fighter jets to the Ukrainian Air Force. But even if that happened, Ukraine would still need trained pilots to fly them.
The supply of Western weapons helps, but you still need an army that knows how to use them.