This is a perfect example of federal priorities and institutional values.
The fedgov would prefer to shoot down a loaded 747 with a missile from an F-16, than see armed pilots. Why? Because the F-16 pilot is a member of the US military, and in the National Command Authority chain of command.
The airline pilot, even if he is military trained and trained and qualified to fire pistols, is not in the fedgov's chain of command.
It's all about control.