(CBS) – Chicago aldermen on Thursday grilled United Airlines city aviation officials about the now-infamous incident at O’Hare Airport when a paying customer was dragged off a full flight.

WBBM Political Editor Craig Dellimore reports.

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John Slater, United’s Vice President of the airline’s Chicago hub, came to City Hall to offer an apology for a debacle seen countless times via social media.

“It was a failure of our system, with many contributing factors leading up to that moment,” he said during a meeting of the council’s Aviation Committee.

Dr. David Dao of Louisville, Ky. refused to get off the full plane Sunday to make room for United employees. City aviation officers were called, and they ended up dragging the man on the floor; Dao ended up bloodied and, his family says, seriously injured.

Veteran Ward 14 Ald. Ed Burke, a former police officer, had tough questions for Slater about forcing people off a plane.

“Is there a policy to inform the passengers of repercussions if they refuse to de-board?” he asked.

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“It’s not a set policy,” Slater responded.

Burke: “So, there is no policy.”

“There is no script for this,” Slater said.

Burke says it’s sad the city could end up paying for the airline’s inability to defuse the situation.

Addressing the city’s Aviation Department, Burke said: “Chicago employees should not be doing the dirty work for the ‘Friendly Skies’ airline.”

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The department has placed the three officers on leave, pending an investigation.