namespace YourNamespace.Entities
{
    public class Passenger
    {
        public int Id { get; private set; }
        public string FirstName { get; private set; }
        public string LastName { get; private set; }
        public string PassportNumber { get; private set; }

        public static Passenger CreateEntity(int id, string firstName, string lastName, string passportNumber)
        {
            return new Passenger
            {
                Id = id,
                FirstName = firstName ?? string.Empty,
                LastName = lastName ?? string.Empty,
                PassportNumber = passportNumber ?? string.Empty
            };
        }
    }
}