A new series of mistakes by air traffic controllers at O'Hare International Airport has plagued one of the world's busiest airports, which already is the subject of a federal safety investigation, officials say. Controllers at the airport made one error Sunday and two Friday, bringing the number of recorded errors at O'Hare this year to 29, officials said Tuesday. By comparison, Atlanta's Hartsfield International Airport has had six errors this year, and Washington's National Airport two. In one incident Friday, two Air Wisconsin jets came near each other when a controller apparently mistakenly gave one of them an order to descend from 14,000 feet to 11,000 feet, a Federal Aviation Administration spokesman said. In the day's other incident, an American Airlines jet and a Delta Air Lines jet came within 400 feet vertically and a mile horizontally when the pilot of the American apparently failed to repeat an order to reduce speed and the controller did not seek confirmation, the Chicago Tribune reported today. On Sunday, two United Airlines jets came within 500 feet of each other horizontally after the pilot of one plane apparently followed an order intended for the other, the newspaper said. The FAA requires airplanes in the area to be separated a minimum of three miles horizontally or 1,000 feet vertically. The incidents occurred just two months after the National Transportation Safety Board issued a report saying that chronic understaffing, mandatory overtime, outdated equipment and inadequate training had contributed to mistakes at O'Hare. And now NTSB officials are worried that the trend has not been reversed, said regional director Carl Dinwiddie. The FAA, which has 90 days to respond to the NTSB report, has not yet replied, said an NTSB spokesman in Washington. Both agencies are investigating the recent errors. Joe Bellino, regional representative of the National Air Traffic Controllers Association, said O'Hare's radar room on Friday was ``a zoo.'' With Friday's 3,842 takeoffs and landings _ 11 below the record set the day before _ there should have been 18 journeyman controllers and several ``developmental'' controllers on duty. But Bellino said there were only 14 controllers in both categories, and the problem was made worse when the controllers who made the errors were temporarily relieved of their duties, giving those who remained even more responsibilities. ``We had airplanes all over the sky,'' Bellino said. ``We were buried all day long.'' The FAA could not immediately say how many controllers were on duty Friday, but spokesman Donald Zochert said the total number of controllers working at the airport has risen from 87 last year to 94 as of Sept. 1. There are now six new developmental controllers and one new journeyman.
