Ukraine has been vastly outmatched by the Russian military in raw numbers and firepower. But the US says Ukraine's airforce is still viable, a demonstration of the government's resilience in the face of Russia's assault.

According to Kiev, Moscow has so far lost at least 39 aircraft and 40 helicopters since the crisis began. According to the Stockholm International Peace Research Institute, Ukraine has 34 attack helicopters versus Russia's 544. Kiev has 98 fighter jets and other attack aircraft while Russia has over five hundred.

Ukraine spends close to nine-percent or six billion dollars on its military. Russia spent 62 billion dollars on its defence forces last year, which is 11-percent of total government expenditure.

Subscribe to our channel for all our latest in-depth, on the ground reporting from around the world.