Memorial Day week-end kicks off the summer air travel season, and officials at Will Rogers World Airport in Oklahoma City say travelers should be prepared. They estimate nearly 60,000 travelers will fly in and out of the airport Thursday through Monday. "Travelers should expect the airport to be busy-from the ticket counters, to the checkpoints to the boarding gates," says spokeswoman Karen Carney. She advises travelers to arrive at least 90 minutes before their flight.