The plane ticket was used as a soothing balm to get Carlo in the car without a fuss (as TB explained). But Carlo was garrotted as the car pulled away and no one was around to witness; they were all at the Baptism party. The real problem. What do the hitmen and Clemenza do now? The windshield of the car is broken - out and they have a body to get rid of. Its daylight, you're on the Corleone mall, which according to the book has other residence. Wait a minute, what are we worried about. These guys got rid of Tessio without a peep. I imagine the car drove in circles in the mall while Clemenza did his thing. He got out and got back in Mike's car. "The boys" then cleaned up the glass, put Carlo in the trunk of another car to take him where the fishes sleep and one of Cicci's boys took the car to the shop to get a new windshield which got hit by a baseball.