This raises another point:

Michael was frantic to get Fredo on that plane out of Cuba. Obviously he wasn't motivated by brotherly love at that point--he wanted Fredo to pump him for more info about the Tahoe shooting plot. And, when Michael arrives back in Nevada (probably less than 48 hours later since he's wearing the same clothes as in Havana, and is exhausted), the first thing he asks Tom is, "Where's my brother?" Tom obviously knows where Fredo is, because he says, "I think he must be in New York." Michael knows Tom knows where Fredo is because he tells Tom, "I want you to get word to Fredo...I know Roth misled him..."

Notice that the sense of extreme urgency has suddenly disappeared. Michael could have ordered Tom to bring Fredo to him directly. Instead, it's "get word to Fredo..." In fact, Fredo's out of the picture until after Michael gets nailed at the Senate hearing--weeks or even months later--when he finally tells Tom, "I want to talk to Fredo." And then Fredo appears, tout-suite.

My question: Why did Michael lose interest in talking to Fredo between the time he returned from Havana, and the Senate confrontation?