//adds an invoice to an airline public static void AddAirlineInvoice(Airline airline, DateTime date, Invoice.InvoiceType type, double amount) { if (airline.IsHuman && GameObject.GetInstance().HumanAirline == airline) { GameObject.GetInstance().AddHumanMoney(amount); GameObject.GetInstance().HumanAirline.AddInvoice(new Invoice(date, type, amount), false); } else airline.AddInvoice(new Invoice(date, type, amount)); }