Question about multimap

[inso85]

Hi everyone :)
I want to display the contents of a complex multimap.
Here is part of the code:

class CPlane {
public:
	string brand;
	unsigned hours;
};

bool operator<(const CPlane &ob1, const CPlane &ob2) { 
	return ob1.brand < ob2.brand; 
}


class CAirtravel { 
public:
	string company, nation;
	map <CPlane, unsigned> plane;
	multimap <string, unsigned> destination;
};

bool operator<(const CAirtravel &ob1, const CAirtravel &ob2) { 
	return ob1.company < ob2.company; 
  }



class CAirport {

	string name;
	unsigned flight;
	multimap <CAirtravel, unsigned> airtravel;
	
public:
void info() {
	multimap <CAirtravel, unsigned>::iterator iair = airtravel.begin();

	for(; iair != airtravel.end(); iair++) {
		
		cout<<"Airport: "<<name;
		cout<<"\nFlight number: "<<flight;
		cout<<"\n\nData of companies:";
		cout<<"\n\nCompany: "<<iair->first.company;
		cout<<"\nNationality: "<<iair->first.nation;

		map <CPlane, unsigned> pl(iair->first.plane);
		map <CPlane, unsigned>::iterator ipl = pl.begin();

		cout<<"\n\nList of company's planes:";

		for(;ipl != pl.end(); ipl++) {
			cout<<"\nBrand: "<<ipl->first.brand;
			cout<<"\nFlight hours: "<<ipl->first.hours;
			cout<<"\nDestinations: "<<ipl->second;
		}

        multimap <string, unsigned> ds(iair->first.destination);
		multimap <string, unsigned>::iterator ids = ds.begin();

		cout<<"\n\nList of company's destinations:";

		for(;ids != ds.end(); ids++) {
			cout<<"\n\nName of destination: "<<ids->first;
			cout<<"\nFlights to "<<ids->first<<": "<<ids->second; 
		}

	cout<<"\n\nNumber of all company's flights: "<<iair->second<<endl<<endl;

	}
		
}	

If you look at function info(), you will notice that it works correctly only if one pair of elements is present in the airtravel multimap.
I think the problem is here:

map <CPlane, unsigned> pl(iair->first.plane);
multimap <string, unsigned> ds(iair->first.destination);

This maps don't change their content after the first cycle.
How can I remove them before the new cycle ?
I want to recreate them at every new cycle and to give them the values of the next airtravel key ?