Having limited jet engine knowledge makes it better for keeping any discussion at an overview level which most readers will find enlightening. It starts at the narrow top of the symmetrical tree and goes down to the spreading branches near the base. The top, has two competing manufacturers, GE and Rolls Royce. Boeing chooses to have two engine makers because it wanted a broad range of customers who had GE or Rolls Royce fleets allowing for a purchase of its 787. Secondly, if an engine became a flawed concept the other engine maker could save the 787 program. Boeing has reached that Plan B status as the Rolls has hit a bump, and it's not as simple as swapping out Rolls Royce for a GE. It's not a literal plug and play change and the ground crew servicing a "Rolls" are not typically trained for both engine makers.
The problem starts with decomposing fan blades which is the workhorse of the jet engine for pushing air through it. Without the blades, the engine simply won't work at any altitude. The blade degradation is a serious issue. Spinning a fan blade is way more effective than spinning sticks when trying to move air.
Below stuff.co.nz photo: Fan Blades halfway there for becoming a major engine failure.
The carbon fiber resins crack apart as optimal RPMs are reached, thus suffering a catastrophic engine power failure and endangering long-range routes on the "C" package engines from Rolls Royce.
MRO Network Photo Below:
The double edge sword view: airlines with Rolls Royce "C's" could face the cost of regrouping with GE engines, thus becoming too cost prohibitive for any operation, stressing an end for a Rolls Royce 787 engine run. Otherwise, it will also have to pay millions for any fix of the Trent 1000 package "C" engines. Starting with ANA. The second option is what is happening at this time. Customers are awaiting a Rolls solution and that may take years while in the meantime, the FAA has ordered those 787's only a 140 minute flight distance to any airport or about twelve hundred miles. Routes need to bend towards airports instead of flying straight towards its long-range destination.
A subproblem is having a Boeing 787 build processes set up for either the GE or Rolls Royce before engines are even mounted on a frame. Customers who already ordered long in advance for its engines on a 787, can opt out of the Rolls Royce easier than it could change it on a wing of an already delivered 787. Furthermore, it doesn't even consider the costs associated with an increased maintenance penalty for tooling and training of ground crews for a different engine.
Customers who have not made an engine decision with its backlogged order status have time to make an engine commitment change. Engines already flying are costly to repair or switch out with another brand, but it once again can be done at a great cost to ground operations for parts and labor already set for Rolls Royce engine maintenance.
Plan A is for Rolls Royce to change out affected parts to the problem with new parts that result in a permanent solution.