The first six supersonic Jas-39 Gripen fighter jets leased from Sweden by the Czech Republic arrived in the country on Monday, the Defence Ministry has said. Eight more are to join the Czech air force by the end of August. The Gripens will be leased for 10 years at a cost of almost 20 billion crowns (850 million dollars), after which the country has an option to buy them or return them to Sweden. The planes will gradually replace the obsolete soviet MiG-21s. The deal, signed in June 2004, commits Sweden to investing 130 percent of the contract's value in so called "off-sets" in the Czech Republic, 20 percent of which will be direct investments in the Czech economy. The lease of the Gripens was approved by former Prime Minister Vladimir Spidla's government last June.