For international flights airlines recommend the presence at the airport at least two hours before the departure of the flight, we calculate almost always a maximum hour of journey when we have to reach airports inside the city (type Linate or Ciampino) or slightly distant type (Fiumicino). If your departure is from a more distant airport like Malpensa, count an hour and thirty of road. So your driver will have to pick you up three or three and a half hours before your flight departs, depending on where you leave from.