I want to be clear that we understand what you are saying.
You have Me.Departure.TabStop = NO and Me. Arrive.TabStop = NO. When you update Me.LstFlightN you want the Me.Departure and Me.Arrive controls (text boxes?) to be updated. You suggest that they do not update unless you set those two controls to .TapStop = YES. Is that your problem description?
If you could do so, set a breakpoint at the Me.Departure = line to see if the event actually fires in the case that you say is failing.
May I assume that the control LstFlightN is some sort of combo or list box? One thing you might try is to change that to the _Click event, which fires next in sequence after the _AfterUpdate event. To be honest, it would make absolutely no sense for a .TabStop on control A to interfere with the operation of control B unless there was something going in the _GotFocus or _LostFocus events.
Also, you suggest that those are actually bound controls. When you use VBA to assert a new value (as opposed to manual entry or update via navigation), the might not show up instantly but you can force it to show up by adding a Me.Repaint after the second line of that routine.
In summary, verify that the event fires in the conditions you describe AND try adding a Repaint AND if nothing else works, try changing to the Click event AND verify that nothing is going on in any Focus-related events.