The Chicago Department of Aviation police officer who dragged Dr. David Dao from his seat aboard a United Express flight last month had just returned to work after serving a five-day suspension for violating department rules, records obtained by the Chicago Sun-Times show.

Officer James Long is among 40 aviation cops who have been suspended from the controversial law-enforcement agency since Jan. 1, 2014, according to the records obtained under the Illinois Freedom of Information Act.

More than half of those cops were suspended for only a day, presumably for minor infractions. But four aviation cops — including one who was suspended for his conduct on four different occasions — were fired.

Dao’s dragging isn’t part of the log of disciplinary cases the Department of Aviation provided to the Sun-Times. However, officials have previously disclosed that Long is one of four officers who have been put on paid leave as the city investigates the incident, as well as whether the controversial, 292-officer aviation police force should remain in existence.

Though the city lists their job titles as “aviation security officers,” the aviation officers have operated as a secondary, uniformed police force at O’Hare for decades. The officers are police-academy trained and have arrest powers, but they do not carry guns. Only in the wake of the Dao incident has the city begun removing the word “police” from their uniforms and vehicles — a move that the union says violates the officers’ contract.

Officer James Long finished his suspension on March 31. The now-infamous dragging incident occurred nine days later at O’Hare Airport.

Exactly what Long did to warrant being suspended in March was unclear. Also unclear was whether he’s fighting that suspension retroactively through his union. The records obtained by the Sun-Times indicate only that Long violated five department rules on Jan. 29, and, as a result, was suspended on March 27.

Those rules were “failing to take action as needed to complete an assignment or perform a task safely,” “inattention to duty,” “incompetence or inefficiency,” “violating any departmental regulations, rules or procedures” and “conduct unbecoming an officer or public employee.”

“CDA has a strong history of ensuring safety at our airports, and our multilayered security approach allows us to ensure that more than a hundred million passengers travel safely through O’Hare and Midway International Airports each year,” mayoral spokeswoman Lauren Huffman said in an emailed statement. “The requested records demonstrate that whenever there is an issue involving any of our security personnel that we work quickly to address it to maintain our high standards of safety for the traveling public.”

A spokesman for Long’s union, Service Employees International Union Local 73, said he was investigating what led to Long being suspended.

The other two officers who boarded the United Express flight with Long and have been placed on leave have otherwise not been suspended since the start of 2014, according to the records.

Long has defended actions aboard Flight 3411, saying he and others were called in response to a disturbance involving two people who were refusing to leave the jet to make room for four airline employees who needed to fly to Louisville, Kentucky, to keep the airline’s schedule moving.

Long said he approached Dao to ask the 69-year-old physician to get off the plane. Long said Dao refused and “folded his arms tightly,” according to a copy of his report obtained by the Associated Press. Long said he reached out to “hold” Dao and was able to pull him away from his window seat and move toward the aisle, but Dao suddenly “started flailing and fighting,” Long wrote.

Dao then knocked Long’s hand off his arm, causing the struggling Dao to fall and strike his mouth on an armrest on the other side of the aisle, according to the report. Long said he then dragged Dao because Dao refused to stand up.

Following the incident, Dao — who suffered facial injuries and a concussion — settled with United for an undisclosed sum.