 Despite these production problems and the fact that the I @-@ 250 had yet even to be submitted for State acceptance trails , an order had been placed for fifty more aircraft on 26 February ( these aircraft have been referred to as the MiG @-@ 13 , which presumably would have been their designation if they had actually entered service ) . A new deadline of 5 July 1946 was set for the delivery of the first pre @-@ production aircraft , but it was stymied , again , for a lack of an engine . By this time seven airframes had been completed , but all lacked engines . The first I @-@ 250 was finally accepted on 8 August and flown for the first time three days later , although its engine seals failed and a number of ignition cables were scorched . The engine replacement and repairs forced the aircraft to miss its scheduled appearance at the Tushino Air Display . It was handed over to the NII VVS ( Air Force Institute ) on 15 September to finally begin its State acceptance tests . All ten aircraft had been delivered by 30 October , although construction number <unk> ( Factory No. 381 , first batch , seventh aircraft ) was used as a static test airframe and <unk> became a static engine testbed . 
