"At the meeting Lochridge discovered why he had been denied access to the viewport information from the Engineering department—the viewport at the forward of the submersible was only built to a certified pressure of 1,300 meters, although OceanGate intended to take passengers down to depths of 4,000 meters. Lochridge learned that the viewport manufacturer would only certify to a depth of 1,300 meters due to experimen…
The sub has already survived multiple dives to 4000 meters, and so far nobody has come out with reports of any apparent problems with the viewport. Maybe it failed from an impact or from accumulated fractures from all these pressure cycles, but I'm also completely willing to believe that the depth-rating for human occupancy has enough of a safety factor that going 3 times deeper doesn't lead to failure. From the pre-…
The goal is to have extremely high reliability at the given rating. Not failing for a half dozen trips is nearly meaningless. Safety critical equipment is expected to meet the rated load thousands of times without issue. Using equipment well outside its rated working load, in situation where failures kill people, is highly irresponsible.