> In this case, the likelihood of a single engine shutdown due to this elusive bug ... _combined with the fact that all commercial aircraft needs to be able to operate with only one of the engines_, makes Boeing ask for the exemption.

That's not very reassuring to me. The article is light on details, but this bug is apparently triggered "during a step climb to a higher altitude in ice crystal icing conditions." The fact that the plane can operate one one engine doesn't do much good if both engines fail due to the same bug because they're experiencing the same conditions at the same time.