MOSCOW - Iran has signed contracts worth $21 billion to buy satellite equipment and aircraft from Russia, Manouchehr Manteghi, the managing director of Iran Aviation Industries Organization, said in an interview with Russian agency Sputnik on Saturday.Manteghi said the contracts had been signed at the MAKS-2015 air show in Russia last month.The contracts involved satellite-related equipment as well as the Sukhoi Superjet 100 regional passenger aircraft, Sputnik said.Russia and Iran have been working to boost economic ties since Tehran signed a deal with six world powers in July, which offers Iran relief from sanctions in exchange for curbing its nuclear program.