I would be very surprised to find that under (various state versions of) US law, there is no such duty.
How does it feel to be surprised this morning? Hopefully it's a good feeling.
Under US theories of tort liability an employee is only liable for his or her own actions (as opposed to the employer) under two conditions. The first condition is when he or she is acting outside "the scope of his employment". This is a very narrow exception because courts have ruled that even driving drunk while on the job is the employers responsibility not the employees'. The other exception is if the activity is otherwise innately criminal, such as an employee who rapes a client. Those are the only two exceptions.
From an American point of view this case is an easy, cut and dried case. Was he acting within the scope of his employment? Obviously, he was an airline mechanic and he was fixing an airplane. Was his action otherwise innately criminal? Nope, nothing illegal about fixing a plane incorrectly. He would not have been punished in the USA.
You might want to read up on the legal aspects of this case: Valujet 592.
ValuJet Flight 592 - Wikipedia, the free encyclopedia
Notice that not a single natural born person was convicted of a crime. But the
company was criminally charged and convicted. That's the way we do it here. And I'd argue that it's philosophically the best way to do thing, chest thumping aside.