D-n-D is from one node to another within the same app.
Something is causing the drag flavour to not make it to the drop target. "placeholder.custom.bytes" seems to be an internal JavaFX flavour. The application works fine on Windows, I don't get the "'application/x-kayak-document' is not a valid UTI string." message.

Drag and Drop fails with the following debug output:

2013-08-16 12:22:52.937 java[25806:2717] 'application/x-kayak-document' is not a valid UTI string. Cannot set data for an invalid UTI.
08-16 12:22:54 WARNING DropAccepter [AWT-AppKit]: Internal error in dropStuff()
java.lang.IllegalStateException: Unhandled drag flavor: [[placeholder.custom.bytes]]
at ca.digitalrapids.kayak.gui.javafx.DropAccepter.dropStuff(DropAccepter.java:88)
at ca.digitalrapids.kayak.gui.javafx.scene.KayakGraphUI$6.handle(KayakGraphUI.java:259)
at ca.digitalrapids.kayak.gui.javafx.scene.KayakGraphUI$6.handle(KayakGraphUI.java:254)
at com.sun.javafx.event.CompositeEventHandler.dispatchBubblingEvent(CompositeEventHandler.java:69)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:217)
at com.sun.javafx.event.EventHandlerManager.dispatchBubblingEvent(EventHandlerManager.java:170)
at com.sun.javafx.event.CompositeEventDispatcher.dispatchBubblingEvent(CompositeEventDispatcher.java:38)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:37)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.BasicEventDispatcher.dispatchEvent(BasicEventDispatcher.java:35)
at com.sun.javafx.event.EventDispatchChainImpl.dispatchEvent(EventDispatchChainImpl.java:92)
at com.sun.javafx.event.EventUtil.fireEventImpl(EventUtil.java:53)
at com.sun.javafx.event.EventUtil.fireEvent(EventUtil.java:33)
at javafx.event.Event.fireEvent(Event.java:171)
at javafx.scene.Scene$DnDGesture.fireEvent(Scene.java:2614)
at javafx.scene.Scene$DnDGesture.processTargetDrop(Scene.java:2810)
at javafx.scene.Scene$DnDGesture.access$6500(Scene.java:2590)
at javafx.scene.Scene$DropTargetListener.drop(Scene.java:2557)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$3.run(GlassSceneDnDEventHandler.java:105)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler$3.run(GlassSceneDnDEventHandler.java:97)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassSceneDnDEventHandler.handleDragDrop(GlassSceneDnDEventHandler.java:97)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleDragDrop(GlassViewEventHandler.java:411)
at com.sun.glass.ui.View.handleDragDrop(View.java:718)
at com.sun.glass.ui.View.notifyDragDrop(View.java:1024)
at com.sun.glass.ui.mac.MacPasteboard._putItemsFromArray(Native Method)
at com.sun.glass.ui.mac.MacPasteboard.putItemsFromArray(MacPasteboard.java:148)
at com.sun.glass.ui.mac.MacPasteboard.putItems(MacPasteboard.java:176)
at com.sun.glass.ui.mac.MacSystemClipboard.pushToSystem(MacSystemClipboard.java:248)
at com.sun.glass.ui.SystemClipboard.flush(SystemClipboard.java:28)
at com.sun.glass.ui.ClipboardAssistance.flush(ClipboardAssistance.java:34)
at com.sun.javafx.tk.quantum.QuantumClipboard.flush(QuantumClipboard.java:197)
at com.sun.javafx.tk.quantum.QuantumToolkit.startDrag(QuantumToolkit.java:1211)
at javafx.scene.Scene$DnDGesture.dragDetectedProcessed(Scene.java:2635)
at javafx.scene.Scene$DnDGesture.process(Scene.java:2696)
at javafx.scene.Scene$DnDGesture.access$8700(Scene.java:2590)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3327)
at javafx.scene.Scene$MouseHandler.process(Scene.java:3151)
at javafx.scene.Scene$MouseHandler.access$1900(Scene.java:3106)
at javafx.scene.Scene.impl_processMouseEvent(Scene.java:1563)
at javafx.scene.Scene$ScenePeerListener.mouseEvent(Scene.java:2248)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:250)
at com.sun.javafx.tk.quantum.GlassViewEventHandler$MouseEventNotification.run(GlassViewEventHandler.java:173)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.quantum.GlassViewEventHandler.handleMouseEvent(GlassViewEventHandler.java:292)
at com.sun.glass.ui.View.handleMouseEvent(View.java:530)
at com.sun.glass.ui.View.notifyMouse(View.java:924)