As the busy Thanksgiving travel week began, two small private planes veered dangerously close to each other because of air traffic control errors, marking the second near miss in the area in less than a week.

The planes traveling over central Wisconsin came within 2.8 lateral miles and 500 vertical feet from each other Saturday. Federal regulations require at least 5 miles of lateral separation and at least 1,000 feet of vertical separation.

"We were not talking to either airplane," said Jeffrey Richards, president of the controllers' union at the Federal Aviation Administration's Chicago Center in suburban Aurora. "This was really a bad situation."

One of the planes, a Cessna Caravan 208 turboprop, had taken off from Chicago's Midway Airport and was traveling to Leeward Farm, a private airport in Soldiers Grove, Wis. The second plane, a Cirrus SR-22, had just departed from the Tri-County Regional Airport near Lone Rock, Wis., when the near miss occurred at about 3,800 feet.

Controllers' union officials blamed years of short staffing and fatigue for last week's errors but said Saturday's mistake occurred after a misunderstanding between controllers at the Aurora center and counterparts in Madison, Wis., about how much air space needed to be blocked off for the Cirrus as it took off.

At the same time, controllers in Aurora switched the landing Cessna to an advisory channel and were unable to communicate with the pilot.

On Nov. 13, an air traffic controller in Aurora mistakenly directed a passenger plane to descend in the path of a jet heading to O'Hare International Airport. The planes came within seconds of a collision over Indiana during a shift change for controllers, officials said.

A collision was averted when a cockpit safety device in one of the planes alerted pilots, who began an emergency climb to get out of the way.

FAA spokesman Tony Molinaro downplayed a connection between the two near misses and noted in a Monday statement that overall errors at the Aurora facility have been decreasing since 2003.

"Two errors in a week at a center does not define a problem. We need to look at it from the proper perspective," he said. "At Chicago Center, they handle about 3 million flights each year, so one or two controller errors in a week does occur."

Control towers are adequately staffed, and Molinaro said federal officials were investigating Saturday's error.