The article did not say how the bad data was introduced. There is plenty of room for contractor malfeasance or incompetence to be a factor. Working around the s

The article did not say how the bad data was introduced. There is plenty of room for contractor malfeasance or incompetence to be a factor. Working around the safety measures in place, for example. Using an import tool improperly. Directly modifying a database through console, or, custom application software written without customer knowledge. Abusing privileged accounts in non-authorized ways. I'm sure there are many more. The engineering precautions in system design always involve trade-offs. There is no perfect system that could be created for acceptable costs. Ultimately it is always going to come down to humans following the rules, hopefully as few of those very-trustworthy humans as possible, though that's where the FAA may have been lax.