Upvote:2
The guys and girls at the check-in desk are allowed a certain level of tolerance. I know that for misspelled names one wrong letter is allowed.
A "forgotten" middle name is usually not a problem either. I know of a couple of cases where did not have their middle names on their tickets and this didn't matter at all.
Only if the names look very different they will have a closer look (call their supervisor) and potentially deny boarding.