"The heroic history of the air force is a chronicle of the courage and valour of military pilots, the selfless work of researchers, designers and test pilots," Putin said in an official Air Force Day message.

His message came just days after the service's commander responded to three crashes in one day with a warning that a lack of flight practice was preventing young pilots from acquiring necessary skills.

Airforce commander General Vladimir Mikhailov on Friday said that Russian air force pilots flew planes for around 40 hours a year, while 80 to 100 hours of flight practice were necessary, Interfax reported.

Mikhailov attributed the crash of a Sukhoi-24 plane in the Chita region of Siberia the previous day to pilot error after the training flight hit a mountain in heavy rain.

Mikhailov said it was important to keep experienced pilots in reserve to let the younger generation acquire more experience.

Also Thursday, an Mi-8 helicopter on a training flight made an emergency landing in the southern Saratov region, injuring all eight on board. The incident was blamed on a mechanical malfunction.

Another Mi-8 helicopter crashed on the same day in the troubled southern republic of Chechnya, allegedly shot down by rebels, killing the pilot and severely injuring two other crew members.

Like the army and navy, Russia's air force has suffered from underfunding, poor training and low morale since the collapse of the Soviet Union.

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