The investigation into the “nut rage” case surrounding Heather Cho, a former senior executive of Korean Air, is entering its final stretch, as prosecutors have asked the court to issue an arrest warrant for her and two more people.

Cho, the eldest daughter of Korean Air CEO and Hanjin Group chairman Cho Yang-ho, was charged with violation of the aviation safety law, coercion and interference with the execution of duty.

Cho forced a Korean Air flight bound for Incheon from New York to return to the gate from the taxiway and had the chief of the cabin crew deplane over her displeasure with the way a flight attendant had served her nuts. Investigation by prosecutors and the Transport Ministry found that Cho had manhandled him.

Since the scandal broke early this month, the wealthy scion’s misbehavior and the patriarchal culture of the family-controlled conglomerate have invited public uproar, which prompted the prosecution and the Transport Ministry to launch an extensive probe.

The investigation resulted in the implication of a Korean Air executive who is suspected of attempting to cover up the incident and an official at the Ministry of Land, Infrastructure and Transport who is accused of leaking information about the ministry’s investigation into the case. Prosecutors have requested arrest warrants for them, too.

Prosecutors said that the ministry official talked by phone about 30 times with the Korean Air executive, surnamed Yeo, who is accused of the cover-up attempt, and sent about 10 text messages to provide him with the information about the ministry’s probe. It should come as no surprise that the official had worked for Korean Air for 15 years before moving to the ministry in 2002.

It also turned out that there was another former Korean Air employee among the six ministry officials who were responsible for investigating the case. So they might have had no qualms about allowing Yeo to sit next to the deplaned steward when the ministry investigators questioned him. One cannot expect a fair, objective investigation under such circumstances.

What really causes concern is that revolving-door employment between the ministry and Korean Air is at a serious level. For instance, 14 of the 16 aviation safety supervisors at the ministry and seven of the 11 staffers in the office that issues aviation licenses worked at Korean Air.

Granted, some expertise is needed in areas like these, but this massive presence of former Korean Air employees in key ministry posts will no doubt foster collusive connections between government regulators and the airline company. What Kim did may be the tip of the iceberg.

We still remember the nation’s shock and outrage when the senior coast guard officer who was in charge of the investigation into the sinking of the Sewol ferry had once worked for the firm from which the operator of the ill-fated vessel was formed. We have hardly learned any lessons from the past.