void ModelA::fly(const Airport &destination)//子类必须实现父类的pure virtual函数.
{
	cout<<"ModelA::fly to"<<destination.getPortName()<<endl;
}
void ModelB::fly(const Airport &destination)
{
	cout<<"ModelB::fly to"<<destination.getPortName()<<endl;
}
void Airplane::fly(const Airport & destination)//父类中的pure virtual函数自己的实现
{
	cout<<destination.getPortName()<<endl;
}