JAVA - 2 maps of 2 objects, adding 1 element(objec) from 1st map to the second object

I have two obejcts: Person and Airticket.
This is Person:

public class Person {

    private String surname;
    private String name;
    private String department;
    private String city;
    private int idPerson;
    private Set<Airticket> personsAirtickets = new TreeSet<Airticket>();

}

This is Airticket:

public class Airticket {
    private int idAirticket;
    private Date date;
    private String from;
    private String where;
    private String class;
    private String airline;
    private int price;
    private int idPassenger;
}

I have 2 CSV files. One file is where persons are stored, second file is where the airtickets are stored.
I read the CSV files and stored the persons and airtickests .... both in a HashMap.

Then I find the airticket for which idPerson == id Passenger.
So, now I want to add this airticket (object) to the TreeMap of person.
How can I do it?

This is what I tried but it doesn't work.

void stickTogether(){
    for (Airticket airtick : getMapAirtick().values()){
        

        int idPassenger2 = airtick.getIdPassenger();
        
        for (Person pers : getMapaPers().values()){
                int idPassenger3 = pers.getIdPerson();
                if (idPassenger2 == idPassenger3) {pers.getPersonsTickets.add(airtick);}

}
}
}