@ SloppyJoe
I think all incidents where doors have opened in flight of modern airliners have been cargo doors where the locks failed.
I could be wrong but I seem to recall that all the incidents of cargo doors opening in flight have occurred as a result of the latches not been fully engaged.
This was due to the doors not been correctly rigged. A failure of maintenance procedures, as opposed to design or equipment failure. A little pedantic perhaps but quite an important distinction, in my opinion at least.
Not an issue on the 737 or MD-80 as those aircraft have inward opening cargo doors.