[nollbit]

That's only true if Boeing was the only manufacturer that builds this category of planes (they are not).

Boeing has an issue in their planes that the A350 doesn't have. So if the price of 787's goes up because it needs to go from unsafe to safe, then airlines can buy A350s instead.

[bcatanzaro]

Or they can buy the 787-10 with the Rolls Royce engine that is already certified. (Check out the article!)

In this case, the problem is with the engine, not with the plane, and the alternative engine is already approved and in service.