sentences:  Recent Russian demands for renegotiation of earlier contracts, the sale of RD-93 engines (a variant of the Klimov RD-33 that powers the Indian MiG-29s) to Pakistan for its JF-17 Thunder aircraft and concurrently supplying combat aircraft to China has also caused concern in New Delhi.The Saab JAS 39 Gripen ("Griffin" or ""Gryphon"") is a fighter aircraft manufactured by the Swedish aerospace company Saab.The aircraft is in service with the Swedish, Czech, Hungarian, and the South African air forces.