The value of LD50 for a substance is the dose required to kill half the members of a tested population after a specified test duration
This is, effectively, how oral flee/tick medications work in animals. It basically turns the animal’s blood into a mild poison. The poison is mild enough that it doesn’t affect the animal but it’s enough to kill small insects like flees, ticks, or mosquitoes.
If the planes had entered sovereign airspace, sure. They synopsis says the Russians were flying in international airspace, which usually means it’s not under the sovereign control of any nation and the Latvians would have had no basis to fire on the Russians.
Personally, I’d love to see the Russians try to stunt their way into someone’s airspace and get dick slapped for it, but I doubt that would happen.