SEATTLE – The Federal Aviation Administration is proposing a $585,725 civil penalty against Corporate Air of Billings, Mont., for allegedly operating a Shorts SD-3-30 twin-turboprop cargo aircraft when it was not in compliance with Federal Aviation Regulations.

The FAA alleges Corporate Air failed to maintain the aircraft under the company’s general maintenance manual, which requires daily post-flight inspections that include examining the exterior skin for corrosion. In addition, the maintenance manual requires structural inspections on the basis of flight hours or flights.

The FAA alleges that Corporate Air operated the aircraft in violation of regulations on at least 81 revenue flights between Dec. 21, 2009 and Feb. 4, 2010 with corrosion that had not been detected during the post-flight inspections. The FAA also alleges that structural inspections were not conducted at the required intervals, between Mar. 16, 2006 and Feb. 3, 2010, in violation of federal regulations.

Corporate Air operates charter and air taxi service under Part 135 of the Federal Aviation Regulations and makes daily feeder cargo flights under contract to a major next-day air package airline.

“Keeping aircraft well-maintained and in good condition must be a top priority for any operator,” said FAA Administrator Randy Babbitt. “All operators must comply with maintenance requirements.”

Corporate Air has 30 days from the receipt of the FAA’s enforcement letter to respond to the agency.