While reading this topic, a couple of questions popped into my head that I hadn't considered before.
I was wondering what Sollozzo would do about the diners, since I would think that a hitman could pose as a customer having dinner. And what would he do about diners coming in midway through his meeting with Michael? It occurred to me that the safest bet would be for Sollozzo to bribe (or threaten) the restaurant owner into letting in only his regular, known customers that night OR to order him to empty the restaurant, leaving only Sollozzo's people posing as diners.

What I can't figure out, though, is IF the restaurant is emptied of all but Sollozzo's people, how did one of Sonny's men, one hour before the meeting, sneak into the restaurant to plant the gun in the bathroom? Wouldn't Sollozzo's men (the "pretend diners") be in place by then to notice a stranger enter the restaurant?

This could mean that my assumption is all wrong. Maybe Sollozzo's men searched the restaurant and then left. But that brings me back to my original question: How could Sollozzo be sure every male diner -- whether already present or arriving afterward -- wasn't a Corleone hitman?
Now there's another question. I thought I had read a past post in which someone said that he noticed Sollozzo nod to or signal one of his men at another table when Michael went to the washroom. I also believe the poster mentioned that the presence of this man was clear in the book.

If there was such a man (and I can't recall seeing one in the movie), why didn't he make a move after Michael killed Sollozzo and McCluskey? Michael stands frozen over the two men's bodies for a fair bit of time, giving Sollozzo's man the opportunity to shoot and kill Michael. Never mind that, why didn't this man of Sollozzo's follow Michael to the washroom in the first place?

Now I know the real reason for all of these apparent "flaws" is dramatic narrative. For the story to progress as FFC & Puzo want it, the Sollozzo-McCluskey shooting has to play out as it does in the movie. But for discussion's sake, is there a logical reason Sollozzo didn't do certain things, or is it just a case of Sollozzo placing too much trust in Michael's civilian status? As Turnbull has observed, there are many cases in the Godfather films of men exhibiting the fatal flaw of underestimating each other. Do you think this was such a case?