 Travel experts say that lower airfares and a stronger dollar are driving up demand. The Saturday before Memorial Day, agents screened about 2.9 million passengers. U.S. credit card balances are ballooning because consumers are doing a lot of borrowing. In fact, according to a new Fed report, U.S. consumer borrowing moved up by the most in May over three months. Total consumer credit increased $11.3 billion, up from a $6.5 billion surge in April. Wall Street economists had expected an $8 billion bump.