A Russian Su-34 fighter-bomber crashed while on a training mission in the southern region of Volgograd on Saturday. The pilots ejected from the aircraft and survived, the Defence Ministry in Moscow said, adding that the jet went down in a deserted area. The aircraft was not equipped with missiles. The ministry blamed an unspecified technical failure. A Mi-28 combat helicopter crashed in the Kaluga region south-west of Moscow on Thursday. Two occupants died in that incident. Russia uses Mi-28s to destroy Ukrainian tanks and armoured vehicles. Russia has lost dozens of aircraft in combat operati…