ANCHORAGE, JAN. 30 -- The Federal Aviation Administration has ordered Ryan Air Service, Alaska's largest commuter airline, to ground all its planes and cease operations following an investigation of the accident-plagued carrier.

Ryan's 30 planes serve 70 communities, most of them accessible only by airplane. Since 1980, Ryan has had 12 accidents in which a total of 30 people died. The most recent accident occurred Nov. 23 in Homer when a twin-engine craft crashed on landing, killing 18.

The FAA order halting all Ryan operations came Friday evening, FAA spokesman Paul Steucke said.

"This action is the result of several recent investigations of the air carrier by FAA, which included several pending violations," he said.

Ryan may resume operations only when it has followed an FAA regimen that involves a reorganization of the company, retraining for all employees, maintenance and inspection of every Ryan-owned airplane.

Ryan's president, Wilfred Ryan Jr., son of the company founder, was required to step down under the FAA order. The company's director of maintenance also was ordered to resign by the FAA.

The new president, John Eckels, vowed to have company planes flying again in a month. But FAA spokesman Steucke, referring to the list of federal conditions that must be met, said, "We don't know how long this program will take."

Federal safety investigators have not yet concluded what caused the November crash at the Homer airport, but National Transportation Safety Board investigators said there was evidence the plane may have been overweight. Steucke said the FAA is still probing allegations that Ryan management ordered pilots to fly overloaded planes.