...... Michael didn't suspect Fredo (there were no "looks").
.....I think that his failure to tell Fredo about the plane earlier was simply FFC's choice to add to the drama of the chaotic New Year's eve scene.
My thoughts.......
I think that Michael did indeed suspect Fredo, along with Rocco and Neri. Difference being that he had no emotional attachment to Rocco or Neri. But being Fredo's brother, he did have an emotional attachment so a part of him didn't want to believe that his own brother would set him up. I believe that Michael was in conflict over Fredo within himself. The cunning smart untrusting side of Michael battling whatever was left of the humane loving side that he had for his brother. The possible truth vs. emotion.
"
Now, one thing that I learned from Pop was to try to think as people around you think. Now on that basis, anything's possible."
And that is why he did NOT tell Fredo earlier about his plan to leave Cuba by plane. He was not going to let his emotions, his love for his brother, cloud his judgement and the possibility that Fredo could have been the traitor at that point.
