public int CalculateHandlingTime() {
    int minutes = 0;
    Gate arrivalGate = arrival.getLanding();
    Gate departureGate = destination.getTakeoff();

    if (arrivalGate.equals(departureGate)) {
      return 20; // assuming they have to unload all baggage and reload the baggage that doesnt
                 // transfer to
      // different planes
    }

    int ag = arrivalGate.getGateNumber(); // to extract the numbers from the gate string
    int dg = departureGate.getGateNumber();

    if (arrivalGate.getGateTerminal().equals(departureGate.getGateTerminal())) // if same terminal
    {
      if (ag < dg) {
        minutes = 20 + dg - ag;
      } else {
        minutes = 20 + ag - dg;
      }
    } else // not same terminal
    {
      minutes = 20 + ag + dg;
    }

    return minutes;
  }