While maintaining their Mexico routes, airlines are awaiting guidelines from the World Health Organization and other authorities as they stay on the lookout for passengers who may have swine flu symptoms. The outbreak of swine flu in Mexico, as well as reports of 20 cases in the U.S., has prompted the Obama administration to announce a public-health emergency. Travel restrictions to Mexico have not been implemented; however, the European Union urged Europeans on Monday to postpone nonessential travel to the U.S. and Mexico. Meanwhile, some airlines have waived change fees for passengers flying through Mexico. No flights have been canceled, however.