Airlines and Airports across the country upgrading security to meet new Federal Aviation Administration rules the wake of this week's terrorist attacks in New York and Washington. Twin Cities-based Northwest Airlines has begun bringing back SOME international flights which were diverted to cities outside of the United States on Tuesday. (Check to make sure) And Minneapolis St. Paul Airport officials say the airport here will be ready to open UNDER HEIGHTENED SECURITY when the FAA permits the resumption of regular scheduled service. But NO ONE knows WHEN that will be.