In one close call, a controller in training who sent two planes within 100 feet of colliding on March 21 had a sleep disorder and was not being treated, authorities said.
Two days later, a different controller was working on only four hours of sleep when he directed a plane to taxi across a runway in front of another plane taking off, according to a National Transportation Safety Board letter to the Federal Aviation Administration.
The controller involved in the second runway incursion told investigators he "was not as sharp as [he] could have been" because he needed about six hours of sleep each night to feel rested--a pattern that is hard to maintain under the controllers' rotating schedule, which gives them shifts at different times of the day, sometimes just eight hours apart. The FAA classified both cases as controller errors.
Safety board investigators also found that some O'Hare controllers and their FAA supervisors had a poor understanding of the need to get enough rest to avoid mental impairment while controlling more than 2,800 takeoffs and landings a day.
"When asked about [O'Hare] controllers' awareness of the need for adequate sleep, one supervisor stated that controllers did not discuss the issue much and were `just used to being tired,'" wrote John Clark, director of aviation safety at the NTSB, in the May 16 letter to Russell Chew, the FAA's chief operating officer.
Clark urged Chew to provide all O'Hare tower personnel with fatigue-awareness training and "emphasize the importance of sleep management."
The safety board examination of O'Hare tower operations identified other major issues that could hamper safety. They include excessive noise and unnecessary conversations in the tower cab that could distract other controllers working traffic; difficulty maintaining attention while performing a specific controller task for long periods; infrequent safety briefings conducted by FAA managers; and inadequate training for some jobs in the busy tower.
FAA officials said they would assess the issues. They said the noise problem would be addressed when controllers who handle planes taxiing between passenger terminals and runways are moved to a raised center island in the 260-foot tower.
"We will analyze the issues that the NTSB team brought up in their report and consider the recommendations," said FAA spokesman Tony Molinaro.
Under a schedule negotiated between the union and the FAA, O'Hare controllers routinely work three different shifts--day, evening and overnight--during a five-day week to avoid burnout that would result from working the busiest times of the day constantly, FAA officials said. The rotation, common among air-traffic controllers nationwide, means a never-ending transition.
Controllers working a 2-to-10 p.m. shift may have to return to work the next day at 7 a.m. Or after completing a shift at 3 p.m., they may be back in the control tower at 11 p.m. to work the overnight shift.
Shift work in the tower
The FAA requires at least eight hours between the end of one shift and the start of another, Molinaro said. There are no specific sleep requirements.
The shift work generally results in nine to 10 hours off for controllers at major hubs like O'Hare, the safety board said. But research suggests that most people need eight to nine hours of uninterrupted sleep to perform optimally, said board spokeswoman Lauren Peduzzi.
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