She felt a sense of freedom and clarity of mind while at the controls of an airplane during the descent and the preparations for landing. It was all a matter of operating the controls so as to keep certain numbers within certain ranges. By the time the jet was skimming the runway at Waco, its speed needed to have been reduced to a figure denoted VREF. This varied with such conditions as temperature, weight of the aircraft, and runway conditions; but anyway it could be calculated from those thirty-year-old tables and there were known procedures for getting the plane’s speed down to that number.