Not only aircraft were shipped to the Soviet Union, they also received thousands of tanks, tens of thousands of trucks, ammunition and hundreds of tons of other supplies. Without all of that materiel, the USSR very well might have folded.
tonnaged shipped to the Soviets
Year Totals
Persian Gulf - Pacific - Atlantic - Black Sea - Arctic > total
1941-- 360,778 - 13,502 - 193,299 - 153,977 > 721,556 > ~2.4%
1942--2,453,097 - 705,259 - 734,020 - 949,711 - 64,107 > 4,906,194 > ~16.1% >> 18.5% of total shipped
1943--4,794,545 - 1,606,979 - 2,388,577 - 681,043 - 117,946 > 9,589,090 > ~31.5% >> 50% of total shipped
1944--6,217,622 - 1,788,864 - 2,848,181 - 1,452,775 - 127,802 > 12,435,245 > ~40.8% >> 90.8% of total shipped
1945--3,673,819 - 44,513 - 2,079,320 - 726,725 - 680,723 > 2,804,556 > 9.2% >> 100% of total shipped