this is my code when i run the code in visual C++ 6 i get the following errors:

--------------------Configuration: flight prog - Win32 Debug--------------------
Linking...
flight prog.obj : error LNK2001: unresolved external symbol "struct flights __cdecl menuii(struct flights)" (?menuii@@YA?AUflights@@U1@@Z)
flight prog.obj : error LNK2001: unresolved external symbol "struct flights __cdecl seat_to_0(struct flights)" (?seat_to_0@@YA?AUflights@@U1@@Z)
Debug/flight prog.exe : fatal error LNK1120: 2 unresolved externals
Error executing link.exe.

flight prog.exe - 3 error(s), 0 warning(s)

I cant seem to figure out wat im doing wrong can some one help me plez id aprciate it !!

#include<stdio.h>
#include<conio.h>

#define cap 250

// the stuct format allows many fils under one name(tag)used with the type def u can make it possible for much more uses
typedef struct
{
char fname[10];
char lname[10];
char address[30];
int phone;
int seat;
int flightnum;
}flights;
flights plane1[cap],plane2[cap],plane3[cap];

flights menuii(flights);
flights perinfo(flights);
flights seat_to_0(flights);
int secfull(int);
int menu(int);

void main()
{
int opt;
do{
printf("****************\n");
printf("* 1 for plane1 *\n");
printf("* 2 for plane2 *\n");
printf("* 3 for plane3 *\n");
printf("* 4 to exit *\n");
printf("****************\n");
scanf("%d",&opt);

if (opt==1)
menuii(plane1[cap]);
else if (opt==2)
menuii(plane2[cap]);
else if(opt==3)
menuii(plane3[cap]);
else if(opt!=4)
printf("Invalid imput please enterone of the options from the menu\n");
}while(opt!=4);


}//end main

flights menuii(flights passmani[cap])
{
int select,i,fcnonsmok,fcsmok,enonsmok,esmok;
fcnonsmok=0;
fcsmok=50;
enonsmok=100;
esmok=175;
select=0;

/* initializes all seats to zero*/
seat_to_0(passmani[cap]);

for(i=0;i<cap;i++)
{

printf("Please enter the corresponding number to where u would like to be seated\n");
printf("*****************************************\n");
printf("* 1 for Smoking First Class *\n");
printf("* 2 for Non somking First Class *\n");
printf("* 3 for Smoking Economy *\n");
printf("* 4 for Non Smoking economy *\n");
printf("*****************************************\n");
scanf("%d",&select);

if(select==1)
{
if (fcnonsmok>=2)
{ secfull(i);
--i;
}
else
{
fcnonsmok=fcnonsmok+1;
passmani[i].seat=fcnonsmok;
perinfo(passmani[i]);
printf("Your seat Number is %d\n",passmani[i].seat);
}
}
else if (select==2)
{
if (fcsmok==100)
secfull(i);
else
{
fcsmok=fcsmok+1;
passmani[i].seat=fcsmok;
perinfo(passmani[i]);
printf("Your seat Number is %d\n",passmani[i].seat);
}
}
else if(select==3)
{
if (enonsmok==175)
secfull(i);
else
{
enonsmok=enonsmok+1;
passmani[i].seat=enonsmok;
perinfo(passmani[i]);
printf("Your seat Number is %d\n",passmani[i].seat);
}
}
else if(select==4)
{
if(esmok==cap)
secfull(i);
else
{
esmok=esmok+1;
passmani[i].seat=esmok;
perinfo(passmani[i]);
printf("Your seat Number is %d\n",passmani[i].seat);
}
}
else
{printf("You enter an invalid input please enter one from the menu a\n");
i=--i;
}
printf("i is %d",i);

printf("\n& #092;n**************************************************************************
*****\n\n");

}//end fight #control
return passmani[cap];
}//end menuii

flights perinfo(flights passmani)
{
printf("Enter the following information\n");
printf("First Name:");scanf("%s",&passmani.fname);
printf("Last Name:");scanf("%s",&passmani.lname);
printf("Address:");scanf("%s",&passmani.address);
printf("Phone#:");scanf("%d",&passmani.phone);

return passmani;
}// end persons info

int secfull(int x)
{int c;
printf(" Sorry but this section is full, do u which to be placed in another section\n");
printf("if you do please enter 1 if not then enter 2\n");
scanf("%d",&c);
if (c==1)
--x;

else if(c==2)
{printf("NEXT FLIGHT LEAVES IN 3 HOURS\n");
}
return x;
}// end section full


flights seat_to_0(flights popseat[cap])
{
int y;
for(y=0;y<cap;y++)
{popseat[y].seat=0;
}
return popseat[cap];
}//end seat_to_0