Comment on "Observation of Superluminal Behaviors in Wave Propagation"
  Mugnai et al. have reported an experiment in which microwave packets appear to travel in air with a speed substantially greater than c. They calculate the group velocity of their packets and find that it agrees with their experimental result. That calculation is incorrect. A correct calculation gives a group velocity less than c. The reported experimental result cannot be reconciled with the Maxwell equations. 
Murray Peshkin (Argonne National Laboratory)