Steve
I have never understood the oft quoted comment that thrust becomes zero. We know that in a level flight, constant speed situation, L=W and T=D. If T is zero then so must be D - but I have yet to see an aircraft that achieves zero drag. At constant speed, level flight, thrust must be a positive number, not zero. In that situation T does not exceed D = if it did the a/c would accelerate until equilibrium was achieved.
Mike