The chief executive and chairman of the board of United Airlines, Jeff Smisek, has quit amid a corruption investigation.
Two other executives of the US's third largest airline also resigned.
According to US media reports, federal authorities are investigating whether Mr Smisek sanctioned a money-losing flight to benefit the head of the Port Authority of New York and New Jersey.
United said that it was cooperating with investigators.
At the time the route operated from Newark, New Jersey, to Columbia, South Carolina, United Airlines 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 Mr Samson was appointed and cancelled it after Mr Samson left the Port Authority.
Oscar Munoz, the chief operating officer CSX Corp, was named Mr Smisek's replacement as CEO.
