It's a bold attack being labelled Ukraine's furthermost assault on Russian territory.
In hitting more than 40 nuclear-capable long-range bombers in an "extremely complex" drone attack, Ukraine's security services say they have destroyed 34 per cent of Russia's fleet of air missile carriers.
But how did the ambush happen, and how has Russia responded?
Here's what we know so far.
Ukraine launches drone attack on Russian bombers
Ukrainian security officials told news agencies on Sunday, local time, that Kyiv's military had hit 41 Russian warplanes across several key air bases.
The ABC has not independently verified the Ukrainian claims.
"SBU drones have hit more than 40 aircraft, including A-50, Tu-95 and Tu-22 M3, causing damage of over $2 billion," the Ukrainian Armed Forces General Staff posted on Telegram.
The Security Service of Ukraine later inflated that figure to $US7 billion ($10.9 billion).
Ukrainian President Volodymyr Zelenskyy praised the "absolutely brilliant" strike and said 117 drones were used to attack Russian bases.
"Russia has had very tangible losses, and justifiably so," he said.
He also hinted at the details behind Ukraine's "longest-range operation" so far.
How did Ukraine pull off the drone attack?
Mr Zelenskyy said it was an operation that took more than a year and a half to prepare.
And in what appeared to be a comment on Ukraine's allies, he said it led to an outcome "produced by Ukraine independently".
A senior US defence official told AP that the US was not given notification before the attack.
Military sources revealed to news agencies it was an "extremely complex" operation, dubbed "Spider's Web", that involved smuggling drones into enemy territory.
According to AP, first-person view (FPV) drones were smuggled into Russia via trucks, where they were then placed into mobile wooden kit houses.
"At the right moment, the roofs of the houses were remotely opened, and the drones flew to hit Russian bombers," the security source told AP.
Retired Major-General Gus McLachlan says Ukraine's "innovation" is something Western military planners should look to.
"Their ability to find innovative ways and adapt these new technologies at very low cost is extraordinary," he told ABC News Channel.
"We think these drones probably cost about $4,000 each.
"I'm sure there was significant costs in setting up these kit homes with retractable roofs, et cetera, but in real terms we're destroying billions of dollars worth of aircraft."
He said there's no doubt the Russian aircraft will be "very hard to replace".
"At very low cost, with extraordinary innovation and adoption of frankly commercial technology, we've seen the destruction of a high proportion of Russia's ability to do deep strikes."
Where did the Ukrainian drone attack in Russia happen?
The drones, clearly targeting prized strategic assets, attacked Russian bases as far north as Siberia.
Russia's Defense Ministry said air bases across five regions were believed to have been targeted.
These are the Murmansk, Irkutsk, Ivanovo, Ryazan and Amur regions.
[map]It said attacks in the airfields of Ivanovo, Ryazan and Amur were repelled.
"In the Murmansk and Irkutsk regions, the launch of FPV drones from an area in close proximity to airfields resulted in several aircraft catching fire," Russia's defence ministry added.
The ministry said the fires were extinguished and no casualties were reported.
Some individuals involved in the attacks were detained, it added.
The attack in the Irkutsk region marks the first time Ukraine has launched a drone assault so far from the front lines, which were more than 4,300 kilometres away.
Among the aircraft Kyiv targeted were Tu-95 and Tu-22M strategic bombers, which Russia uses to fire long-range missiles at Ukraine.
What has Russia said?
We're yet to hear from Russian President Vladimir Putin.
But already, aviation experts have labelled it a "black day" for Russia's war efforts.
Ukrainian expert Valeriy Romanenko says war analysts will be able to look at the extent of the damage with satellite images.
"Then we will be able to assess the results of this strike and determine how painful this attack was for the Russians," he told Reuters.
"But it is already clear that today was a black day for Russian aviation."
Mr Romanenko also noted that it was a "powerful strike on huge strategic bomber planes" made by "tiny, cheap drones".
"Every type of military equipment has its weak spots," he added.
"For planes, the weak spots are the fuel tanks.
"If a drone lands on top of a fuel tank and a tiny cumulative charge explodes and pierces the tank, we would see what we saw today in Olenegorsk and Belaya."
What happens now?
Russia and Ukraine are set to head to Türkiye for more peace talks.
Russia also says it has received Ukraine's draft memorandum for a peace accord, according to Russian news agencies citing Kremlin aide Vladimir Medinsky.
In a statement on Telegram, Mr Zelenskyy said Ukrainian Defence Minister Rustem Umerov would lead Kyiv's delegation on Monday, local time.
"We are doing everything to protect our independence, our state and our people," he said.
ABC/wires
