The Trent 500 is certified at 60,000 lb of thrust and derated to 56,000 lb for the A346, and 53,000 lb for the A345. Thrust-wise, it would meet the need of a B744. But the Trent 500 has a much larger fan. To fit the Trent 500 on a B744 would need a lot of modifications. Rolls is proposing another derivative, the Trent 600, for the B744XQLR. Boeing has yet agree to offer a brand new engine on the new B744 derivative due to additional development costs. Cathay is most definitely interested in a Trent 600 version of the B744XQLR. We just have to wait and see.