They haven't been .. Boeing was ordered to correct the problem by Jeffrey E. Duven and the order was filed just a few months ago (11-15-13)
The problem was addressed in 2012 - it took a year for the problem to even be addressed by the FAA in an official capacity ... there has been no report from Boeing about correcting the problem.
There is no wreckage from the plane, it just disappeared and a Malaysian official claimed it was spotted on military radar an hour after the transponders stopped sending signals.
Since no one knows what happened, and we are all just guessing ... my guess it was hijacked.
