Three South Australian jockeys have been fined and suspended for one month after misbehaving on a commercial flight from Adelaide to Mount Gambier.

Jockeys Garry Hoobin, Paul Marks and Sean Harrison fronted TRSA stewards yesterday, after an incident on June 23.

Stewards deemed their actions on the flight were "prejudical to the image of racing" and subsequently charged them under the rule of AAR.175A.

Hoobin and Marks pleaded guilty while Harrison offered no plea.

After deliberating, stewards suspended all riders for one month commencing at midnight on Sunday, 19 July 2009 and in addition, each rider was fined $500 and received a year ban from all Regional Express flights.

It is understood the riders brought twelve beers on the Regional Express flight and despite the pleadings of airline staff not to open them, proceeded to consume the alcohol.

Ironically, the trio were returning from an industry-funded tutorial about responsible consumption of alcohol.

It is also believed Paul Marks is under investigation from the Civil Aviation Authority for allegedly failing to wear a seatbelt during the flight.

All riders have been informed of their right to lodge an appeal.