United Airlines chairman and CEO Jeff Smisek has resigned amid a corruption investigation.

Two other executives of the US’s third largest airline also quit.

According to media reports, federal authorities are investigating whether Jeff Smisek sanctioned a money-losing flight to benefit the head of the Port Authority of New York and New Jersey.

United Airlines said that it was cooperating with investigators.

At the time the route operated from Newark, New Jersey, to Columbia, South Carolina, United was lobbying for improvements at Newark Liberty International Airport, which the Port Authority owns.

Former Port Authority Chairman David Samson owned a vacation home in Columbia at the time.

United launched the twice weekly, direct flight route shortly after David Samson was appointed and canceled it after he left the Port Authority.

Oscar Munoz, the chief operating officer CSX Corp, was named Jeff Smisek’s replacement as CEO.