The second modification program retrofitted 500 KC-135 'Stratotankers' with new F108 high-bypass turbofan engines produced by General Electric and Snecma. Capable of producing approximately 22,500 lbf of thrust, nearly a 100% increase in thrust compared to the original J-57 engines. The modified tanker, designated KC-135R (modified KC-135A or E) can offload up to 50% more fuel, is 25% more fuel efficient, costs 25% less to operate than. It is also significantly quieter than the KC-135A, with noise levels at takeoff reduced from 126 to 99 decibels. The KC-135R's operational range is 60% greater than the KC-135E for comparable fuel offloads, providing a wider range of basing options.