The Mexicana Airlines ticket counter is seen without customers for a flight to Mexico City Monday, April 27, 2009, at San Francisco international airport in San Francisco. President Barack Obama appealed for calm Monday as officials revealed there were 40 confirmed cases of deadly swine flu across the US and warned against non-essential travel to neighboring Mexico. Friday, Continental Airlines announced it was temporarily canceling its Mexico service.(AP Photo/Ben Margot)
Read the article: Swine flu cases exceed 140 in U.S.