In the output part, the pointer loses its place

struct custom{
    custom* pLink;
    custom* pToFl;
    string name;

};
typedef struct portNode{
    int numberOfCus = 0;
    string flightName;
    custom headerNode;
    portNode* pLink;
}flight;

struct airport{
    int numberOfPort = 0;
    flight headerNode;
};

airport* createAirport(){
    airport* pReturn = NULL;

    pReturn = (airport*)malloc(sizeof(airport));

    if(pReturn != NULL){
        memset(pReturn, 0, sizeof(airport));
    }
    else{
        cout << "Memory allocation failure" << endl;
        return NULL;
    }
    return pReturn;
}

void addFlight(airport* pList, string newFlightName){
    flight* pNewFlight = NULL;
    flight* pPreNode = NULL;

    if(pList != NULL){
        pPreNode = &(pList->headerNode);
        while(pPreNode->flightName != newFlightName){
            if(pPreNode -> flightName != newFlightName && pPreNode -> pLink == NULL){
                pNewFlight = new flight;
                pNewFlight -> flightName = newFlightName;
                pNewFlight -> pLink = NULL;

                pNewFlight -> pLink = pPreNode -> pLink;
                pPreNode -> pLink = pNewFlight;
            }
            pPreNode = pPreNode->pLink;
            pList->numberOfPort++;
        }
    }
}

void addCustomer(airport* pList, string newFlightName, string newName){

custom* pNewCustom = NULL;
    custom* pPreNode = NULL;
    flight* pNewFlight = NULL;

        pNewCustom = new custom;
        if(pNewCustom != NULL){
            pNewCustom -> pLink = pNewCustom;
            pNewCustom -> pToFl = pNewCustom;
            pNewCustom -> name = newName;

            pNewFlight = &(pList->headerNode);

            while(pNewFlight->flightName != newFlightName){
                pNewFlight = pNewFlight -> pLink;
            }

            pPreNode = &(pNewFlight->headerNode);


            pNewCustom -> pToFl = pPreNode;
            pNewCustom -> pLink = pPreNode -> pLink;
            pPreNode -> pLink = pNewCustom;
        }
    }
}

----------------------------------------
void displayCustomer(airport* pList, string newFlightName){

flight* pNode = NULL;
custom* pCustom = NULL;

if(pList != NULL){
    pNode = (pList->headerNode.pLink);

    while(pNode->flightName != newFlightName){
        pNode = pNode -> pLink;
    }
    pCustom = pNode->headerNode.pLink;
    }
while(pCustom -> pLink != pCustom){

-----This is where the problem occurs--------

cout <<pCustom->name <<endl; //where Thread 1: EXC_BAD_ACCESS (code=1, address=0xc) ##Error code appears
    pCustom = pCustom->pLink;
}

int main() {
    airport* pList = NULL;
    int choice;
    string portName;
    string name;

    pList = createAirport();

    while(true){
        cout << "CHOICES:\n";
        cout << "1. Add an Airport\n";
        cout << "2. Find an Airport - Standard Looping\n";
        cout << "3. Exit Program\n";
        cout << "Enter your choice: ";
        cin >> choice; cout << "\n\n";

        switch(choice){
            case 1: cout << "Inserting Airport\n";
                cout << "portName: " << endl;
                cin >> portName;
                addFlight(pList, portName);
                cout << "name: " << endl;
                cin >> name;
                addCustomer(pList, portName, name);
                break;
            case 2: cout << "Finding Airport\n";
                cout << "portName: " << endl;
                cin >> portName;
                displayCustomer(pList, portName);
                break;
            case 3: cout << "Terminating......\n";
                exit(EXIT_SUCCESS);       break;
            default: cout << "Not Valid\n\n";break;
        }
    }
}