Pre_Flight* create_pre_flights_header_list(void){

    Pre_Flight *node;
    node = (Pre_Flight*) malloc(sizeof(Pre_Flight));

    if(node != NULL){
        ode->airplane.flight_code=0;
        node->airplane.init=-1;
        node->airplane.takeoff=-1;
        node->airplane.eta=-1;
        node->airplane.fuel=-1;
        node->next = NULL;
    }
    return node;
}

void insert_pre_flight(int fc,int init,int to, int eta, int fuel){
    Pre_Flight *node = create_pre_flights_header_list();
    Pre_Flight *first;
    node->airplane.flight_code = fc;
    node->airplane.init = init;
    node->airplane.takeoff = to;
    node->airplane.eta = eta;
    node->airplane.fuel = fuel;

    if(preflights->next == NULL || node->init < preflights->next->init) {
        node->next = preflights->next;
        preflights->next = node;
    }
    else {
        first = preflights;
        while(first->next != NULL && first->next->init < node->init) {
            first = first->next;
        }
        node->next = first->next;
        first->next = node;

    }
}

Pre_Flight* removeInPreFlightList(){
    Pre_Flight *tmp = preflights->next;
    if(preflights->next == NULL) {
        return NULL;
    }
    else {
        if(tmp->next == NULL) {
            preflights->next = NULL;

        }
        else {
            preflights->next = tmp->next;
            tmp->next=NULL;
        }
        return tmp;
    }
}

int emptyLists() {
    if(preflights->next == NULL && flights->next == NULL) {
        return 1;
    }else {
        return 0;
    }
}

Flight* create_Flight_header_list(void){

    Flight *node;
    node = (Flight*) malloc(sizeof(Flight));

    if(node != NULL){
        node->currentF.flight_code = fc;
        node->currentF.init = init;
        node->currentF.takeoff = to;
        node->currentF.eta = eta;
        node->currentF.fuel = fuel;
        node->next = NULL;
    }
    return node;
}

void insert_Flight(int fc,int init,int to, int eta, int fuel){
    Flight *node = create_Flight_header_list();
    Flight *first;
    node->currentF.flight_code = fc;
    node->currentF.init = init;
    node->currentF.takeoff = to;
    node->currentF.eta = eta;
    node->currentF.fuel = fuel;

    if(flights->next == NULL || node->init < flights->next->init) {
        node->next = flights->next;
        flights->next = node;
    }
    else {
        first = flights;
        while(first->next != NULL && first->next->init < node->init) {
            first = first->next;
        }
        node->next = first->next;
        first->next = node;
    }
}