Pratt is basing its 777X bid on a geared concept designated the PW1095G or PW10100G, depending on which side of the 100,000-lb.-thrust line the final configuration ends up. The engine will have a fan-drive gear system with a gear ratio around 3.5:1 and a fan diameter that will likely be slightly larger than the 128 in. of the GE90-115B. Target bypass ratio could be as high as 15:1.

Rolls-Royce is proposing the RB3025, which is targeted at a fuel burn more than 10% lower than the GE90-115B. Overall pressure ratio will be around 62:1 with a bypass ratio of 12:1, compared with 7.08:1 for the big GE engine. The concept builds on the company's technology programs, as well as the Trent XWB engine being tested for the A350, and would be the first large Rolls engine to incorporate composite fan blades and casing.