void bubblesort()
{
int i;
int	j;
int	z;
char aux[MAX_LENGTH];
for (i= 1; i< n_airports; i++)
	for (j = n_airports-1; j >= i; j--)
		if (strcmp(airports[j-1].name, airports[j].name) == 1)
		{
			
			strcpy(aux, airports[j-1].name);
			strcpy(airports[j-1].name, airports[j].name);
			strcpy(airports[j].name,aux);

			z = airports[j-1].x_coord;
			airports[j-1].x_coord=airports[j].x_coord;
			airports[j].x_coord = z;	

			z = airports[j-1].y_coord;
			airports[j-1].y_coord=airports[j].y_coord;
			airports[j].y_coord = z;	
		}

}