I've always thought that what really matters in engineering is not which mistakes you make, its which you CATCH, are you able to admit to them and how you FIX them? -- SkepikI

It depends on the timing. During the design and development process, improvements are made, sometimes rectifying mistakes. Once you say it's ready for production, it's never time to say "what really matters in engineering is not which mistakes you make, it's which you CATCH". Mistakes reaching the customer are never acceptable. Sometimes it's inconvenient, sometimes it's fatal. I'm sure the crew on the Challenger would agree.

Rob