I think you're misunderstanding what an airworthiness certificate is. It is a document issued by the FAA to the registered owner of the plane. The manufacturer is not involved.
I'd guess you're thinking of the type certificate.
I'd guess you're thinking of the type certificate.
Delta has its own CAMO (Delta TechOps), which I assume has done the maintenance of this aircraft, but it is yet to be seen whether they followed everything to the T or is there something missing from Boeing’s part.
As I said in another comment, I doubt everyone here (which is not bad, it’s just not assuming by default that everything is well done everywhere) and will wait for the FAA report.