For the following class, I have a test class with two methods. The second method is failing at System.assert(`Jet2.Status__c == 'Booked'`). The status is still 'Active.' How do I fix this?

**Trigger**

    trigger ReservationTrigger on Reservation__c (after insert, after update) {
        
        Set<Id> JetIds = new Set <Id>();
        List<Jet__c> JetsToSave = new List<Jet__c>();
        List<APEX_Invoice__c> invoicesToSave = new List<APEX_Invoice__c>();
        Map<Id, Jet__c> Jets = new Map<Id, Jet__c>();
        
        //Go through and if we find the reservation that is marked as Paid,
        //Then make the Jet booked
        //
        
        if(Trigger.isUpdate){
        
            for(Reservation__c res: Trigger.new){
                if(res.paid__c != Trigger.oldMap.get(res.id).paid__c && res.paid__c == true){
                    JetIds.add(res.Jet__c);
                }
            }
            
            if(!JetIds.isEmpty()){
                for(Jet__c Jet: [select id,Status__c from Jet__c where id in : JetIds]){
                    Jet.Status__c = 'Booked';
                    JetsToSave.add(Jet);
                }
                
                update JetsToSave;
            }   
        }
        
        if(Trigger.isInsert){
            //Go through the list of reservations and get all of the related jets
            for(Reservation__c Res: Trigger.New){
                Jets.put (Res.Jet__c, null);
            }
            
            //Now go through the list of jets and add the data into the map
            for(Jet__c Jet: [select Id, Base_Cost__c, Cost_Per_Nautical_Mile__c from Jet__c where Id in :Jets.keySet()]){
                Jets.put (Jet.id, Jet);
            }
            
            //Go through the list of reservations and create the invoices to write
            for(Reservation__c Res: Trigger.New){
                
                //Which jet are we using for this reservation
                Jet__c Jet = Jets.get(Res.Jet__c);
                Decimal TotalAmount = Jet.Base_Cost__c + Jet.Cost_Per_Nautical_Mile__c * Res.Nautical_Miles__c;
                APEX_Invoice__c Inv = new APEX_Invoice__c();
                Inv.APEX_Customer__c = Res.APEX_Customer__c;
                Inv.Reservation__c = Res.Id;
                Inv.APEX_Amount_Paid__c = TotalAmount;
                
                invoicesToSave.add(Inv);
            }
            insert invoicesToSave;
        }
    }

**Test Class**

    @isTest
    public class ReservationTriggerTestClass {
    
        static testMethod void testCreateInvoices(){
            
            Jet__c Jet = new Jet__c(Name 					  = 'TestJet1',
                                    Base_Cost__c  			  = 1000,
                                    Cost_per_Nautical_Mile__c = 10,
                                    Status__c                 = 'Active');
            
            APEX_Customer__c Cus = new APEX_Customer__c(Name = 'TestCustomer');
            
            insert Jet;
            insert Cus;
            
            Reservation__c Res = new Reservation__c(Jet__c            = Jet.id,
                                                    APEX_Customer__c  = Cus.id,
                                                    Nautical_Miles__c = 50,
                                                    Paid__c           = false);
            
           
            Test.startTest();
            insert Res;
            Test.stopTest();
            
            //Check that the invoice was created and the related to the right records
            //
            
            APEX_Invoice__c Invoice = [select id, Reservation__c, APEX_Customer__c, APEX_Amount_Paid__c
                                  from APEX_Invoice__c
                                  where APEX_Customer__c = :Cus.Id
                                  and Reservation__c = :Res.id];
            
            System.assert(Invoice.APEX_Amount_Paid__c == 1500);
    
        }
        
        static testMethod void testUpdateReservation(){
            
            Jet__c Jet2 = new Jet__c(Name 					  = 'TestJet2',
                                    Base_Cost__c  			  = 1000,
                                    Cost_per_Nautical_Mile__c = 10,
                                    Status__c                 = 'Active');
            
            APEX_Customer__c Cus = new APEX_Customer__c(Name = 'TestCustomer2');
            
            insert Jet2;
            insert Cus;
            
            Reservation__c Res = new Reservation__c(Jet__c            = Jet2.id,
                                                    APEX_Customer__c  = Cus.id,
                                                    Nautical_Miles__c = 50,
                                                    Paid__c           = false);
            
            Test.startTest();
            
            insert Res;
            Jet2 = [select id, status__c from Jet__c where Id = :Jet2.id];
            System.assert(Jet2.Status__c == 'Active');
            Res.Paid__c = true;
            update Res;
            System.assert(Jet2.Status__c == 'Booked');
            
            Test.stopTest();
    
        }
    }