Why does Putin have to travel with no less than four aircrafts?
The main thing is security. All the planes are ready, and Putin gets on one. No way to sabotage his plane, unless all 4 are sabotaged. It is not paranoia, if they are actually out to get you.
“The Russian president has a squad of four of the planes to choose from for security reasons. As soon as knowledge of an international flight is public, all four aircraft are readied for departure but the specific plane to be used by Putin is not known until takeoff. After the choice is made, either one or all three of the remaining planes follow the president as the reserve.”
This is not unusual, and the US President, for example, always travels with a fighter escort.