Shuttle Endeavour

NASA says the nicely sized hunk of missing tile in Endeavour's wing poses no significant threat.
They say they have a week of research and testing to back this up.

My memory may be faulty here...
But I think they said the same thing about Columbia.

My memory may be faulty here too...
But I recall spending three days in the field helping pick up the parts from the tragedy that there was little risk of.