Bug squashing! Crash while trying to pass data entered on detail view to table view controller

#import <UIKit/UIKit.h>
#import "FPLFlightEvent.h"

@interface FPLLogFlightViewController : UIViewController

@property (strong, nonatomic) FPLFlightEvent *flightEvent;

at end. (not really in my code, treehouse forums auto user find function is killing me here)

#import "FPLLogFlightViewController.h"


@interface FPLLogFlightViewController ()
@property (weak, nonatomic) IBOutlet UITextField *departureField;
@property (weak, nonatomic) IBOutlet UITextField *arrivalField;
@property (weak, nonatomic) IBOutlet UITextField *totalFlightTimeField;
@property (weak, nonatomic) IBOutlet UITextField *flightDateField;

@property (weak, nonatomic) IBOutlet UIBarButtonItem *doneButton;

@end

@implementation FPLLogFlightViewController

- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    if (sender != self.doneButton) return;

    if (self.departureField.text.length > 0) {
        self.flightEvent = [[FPLFlightEvent alloc] init];
        self.flightEvent.departureAirport = self.departureField.text;
        self.flightEvent.arrivalAirport = self.arrivalField.text;
        self.flightEvent.totalFlightTime = self.totalFlightTimeField.text;
    }
}

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {

    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];    

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
}

@end

#import <UIKit/UIKit.h>
#import "FPLFlightEvent.h"

@interface FPLTableViewController : UITableViewController

- (IBAction)unwindToLogbook:(UIStoryboardSegue *)segue;

@end

#import "FPLTableViewController.h"
#import "FPLFlightEvent.h"
#import "FPLLogFlightViewController.h"

@interface FPLTableViewController ()

@property NSMutableArray *flightEvents;

@end

@implementation FPLTableViewController


- (IBAction)unwindToLogbook:(UIStoryboardSegue *)segue
{
    FPLLogFlightViewController *source = [segue sourceViewController];
    FPLFlightEvent *flightEvent = source.flightEvent;

    if (flightEvent != nil) {
        [self.flightEvents addObject:flightEvent];
        [self.tableView reloadData];
    }
}

- (id)initWithStyle:(UITableViewStyle)style
{
    self = [super initWithStyle:style];
    if (self) {
        // Custom initialization
    }
    return self;
}

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Uncomment the following line to preserve selection between presentations.
    // self.clearsSelectionOnViewWillAppear = NO;

    // Uncomment the following line to display an Edit button in the navigation bar for this view controller.
    // self.navigationItem.rightBarButtonItem = self.editButtonItem;

    FPLFlightEvent *flight1 = [[FPLFlightEvent alloc] init];
    flight1.departureAirport = @"KRNM";
    flight1.arrivalAirport = @"KNYL";
    flight1.totalFlightTime = @"1.1";
    flight1.flightDate = @"12 Feb 2013";

    FPLFlightEvent *flight2 = [[FPLFlightEvent alloc] init];
    flight2.departureAirport = @"KNYL";
    flight2.arrivalAirport = @"KRNM";
    flight2.totalFlightTime = @"0.9";
    flight2.flightDate = @"13 Feb 2013";

    FPLFlightEvent *flight3 = [[FPLFlightEvent alloc] init];
    flight3.departureAirport = @"KRNM";
    flight3.arrivalAirport = @"KVNY";
    flight3.totalFlightTime = @"1.1";
    flight3.flightDate = @"14 Feb 2013";

    FPLFlightEvent *flight4 = [[FPLFlightEvent alloc] init];
    flight4.departureAirport = @"KVNY";
    flight4.arrivalAirport = @"KRNM";
    flight4.totalFlightTime = @"1.0";
    flight4.flightDate = @"15 Feb 2013";


    FPLFlightEvent *flight5 = [[FPLFlightEvent alloc] initWithDeparture:@"KRNM" andArrival:@"KNYL"]; //designated initializer
    flight5.totalFlightTime = @"2.0";
    flight5.flightDate = @"24 Feb 2014";

    FPLFlightEvent *flight6 = [FPLFlightEvent flightEventWithDeparture:@"KRIV" andArrival:@"KNID"]; //convienence contructor
    flight6.totalFlightTime = @"1.7";
    flight6.flightDate = @"28 Feb 2014";


    self.flightEvents = [NSMutableArray arrayWithObjects:flight1, flight2, flight3, flight4, flight5, flight6, nil]; //loads dummy initial data

}

- (void)didReceiveMemoryWarning
{
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

#pragma mark - Table view data source

- (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView
{
    // Return the number of sections.
    return 1;
}

- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
{
    // Return the number of rows in the section.
    return self.flightEvents.count;
}

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
    static NSString *CellIdentifier = @"LogbookPrototypeCell";

    UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier forIndexPath:indexPath];

    FPLFlightEvent *flightEvent = [self.flightEvents objectAtIndex:indexPath.row];

    cell.textLabel.text = flightEvent.flightDate;

    cell.detailTextLabel.text = [NSString stringWithFormat:@"%@ to %@", flightEvent.departureAirport, flightEvent.arrivalAirport ];

    return cell;
}
@end