Ilyushin began construction of another prototype to evaluate this solution and this was endorsed on 16 October 1954 when the Council of Ministers ordered production to begin at Factory ("Zavod") No. 168 at Rostov-on-Don of the improved version, designated as the Il-40P. The Il-40P prototype first flew on 14 February 1955 and began State acceptance trials on 12 October 1955. The changes had resolved all the problems suffered by the earlier design and an order for a first batch of forty production machines was placed.