A Southwest Airlines pilot was removed from the cockpit ahead of Wednesday's flight from Savannah, Georgia, to Chicago's Midway Airport and was booked with driving under the influence (DUI), according to reports in American media on Thursday.
The pilot's bail was set for $3,500, the reports add.
A Transportation Security Administration (TSA) officer smelled alcohol on the pilot and informed law enforcement, according to a source quoted by NBC.
The flight was delayed by almost five hours due to Southwest Airlines searching for a replacement pilot, according to a report by ABC.
Federal Aviation Administration (FAA) regulations prohibit pilots from using alcohol while on duty, including while flying or attempting to fly an aircraft within eight hours of consuming alcohol or if their blood alcohol concentration reaches 0.04% or higher, according to the reports.
The airline apologized for the disruption and said customers were moved to other flights.
Transport Department sues Southwest
The US Department of Transportation (DOT) announced a lawsuit against Southwest Airlines for operating "multiple chronically delayed flights and disrupting passengers' travel" on Wednesday.
A "chronically delayed flight" is one flown at least 10 times a month which arrives late on more than 50% of flights, according to DOT rules.
Southwest Airlines' stock price fell by 4.47% on Thursday morning in the aftermath of DOT's announcement, according to a report by AFP.