I believe what Mike is trying to say is:
How can the creature evolving randomly evolve upon the exact trait that will further evolve it to be able to fly.
That's like picking an identical ticket out of a pile of 3 billion completely different tickets each time you stick your hand in the pile.
So strangely by defying the odds... it evolves upon the previous trait it just evolved upon.
Not sure if that is the point he was trying to make, but I think the point you are raising is this -
"Arms do not become wings in a single generation, if dinosaurs did become birds, then how did arms slowly change over many generations to finally become fully functioning wings'
i.e. how do apparently fully developed features appear.
Well, I think there are a number of points to this.
There are two main aspects at work - random mutation, and natural selection. Every time a new animal is born, there is a small chance that they will have a small mutation making them slightly different - perhaps their hind legs are more developed, their arms are shorter, their eyes are slightly closer etc. This mutation has a chance to A. make them better able to survive in their environment, B. make them less able to survive in their environment or C. make no difference to their ability to survive in their environment.
If it is A, then over time it is likely that that trait will become dominant in their species.
If it is B. then it is likely individuals with this trait will die out and it will cease to exist.
If it is C. then it may die out, or it may hang around.
The question seems to suggest that 'arms are useful, wings that give flight are useful, so what are the chances of enough random mutations of type C hanging around long enough until they become wings' - but that is not taking into consideration that there are many useful steps in between arms and wings - there are animals that glide using flaps of skin for example.
For more information, goggling the evolution of the eye is very interesting, and it shows how different beings sense light, from very basic photo sensitive cells to eyes such as you and eye are using right now. It does not take a lot of imagination to place these into 'steps'.