Even NASA years into their existence has suffered catastrophic fatal failures. Even with the best and most knowledgeable experts working on it we are ultimately still in the infancy of space flight. Just like airlines every incident we try and understand the cause and prevent it from happening again. Lastly what they are doing is incredibly difficult with probably thousands of things that could go wrong. I think they are doing an amazing job and hope one day, even if I miss it, that space flight becomes acceptable to all who wish to go to space.

I you are referring to the two Space Shuttle accidents, both of them could have been avoided with just a little bit more care - not launching in freezing temperatures for Challenger, and making sure insulation foam doesn't fall off the tank for Columbia.