The startling increase in the number of Covid-19 cases in the United States, Europe and some other parts of the world appears to be denting not only the pace of travel’s recovery but also the attitudes toward it. Airlines Recovery Corp. sales figures show a reversal of positive trends, while travel suppliers’ pessimism is on the rise, and British business owners don’t appear eager to see employees take to the skies again. Meanwhile, Hertz detailed the effect of the pandemic on its on-airport rental volume.