President Putin has sacrificed thousands of tanks and tens of thousands of men in an effort to grind Ukraine into submission. Yet so far he has appeared reluctant to use planes and helicopters to win the battle for the skies.
Barrages of cruise and ballistic missiles have been the main way Putin has sought to press the Russian aerial advantage, while holding his expensive aircraft in reserve. A Russian SU-35 fighter typically costs about £35 million.
The SU-25 Soviet era ground attack fighter-bomber pictured has not fared especially well to date with numerous reports of shoot-downs.
