SAN FRANCISCO — Three San Francisco Bay Area families have sued Boeing over the deadly crash of Asiana Airlines Flight 214, alleging that coach passengers suffered more serious injuries than business class travelers because of different seatbelt configurations.

The lawsuits filed Thursday in federal court in San Francisco say some coach passengers wearing only lap belts suffered head and spinal injuries that could have been prevented by shoulder restraints available in the more expensive and roomy business class seats toward the front of the airliner.

The lawsuits also claim that Asiana failed to properly train its pilots, and that the plane's auto-throttle was inadequate.

Several other lawsuits have been filed on behalf of survivors of the July 6 crash landing at San Francisco International Airport that killed three people and injured 180 others.

Passengers toward the rear of the Boeing 777 took the brunt of the impact when the plane slammed into a seawall at the end of the runway, breaking off the landing gear and ripping off the tail.

The cases filed Thursday were the first questioning the airplane's seatbelts.

The lawsuits, filed by attorney Frank Pitre, seek unspecified damages from Asiana and Boeing. Pitre was expected to file another lawsuit Friday on behalf of a fourth family.

Boeing spokesman Marc Birtel has said the Federal Aviation Administration mandates seatbelt setups on planes. Further, Boeing buys its seats and seatbelts from several different subcontractors and simply installs them on planes, he said.

The airline industry has said adding three-point seatbelts to airplanes would require major changes to seat design that would mean higher airfares and less comfort.

Some business class seats have added a type of shoulder restraint, but those seats are more like beds and often don't face forward.

Days after treating dozens of survivors, Dr. Geoffrey Manley, neurosurgery chief at San Francisco General Hospital, said he was surprised by a pattern of injuries to coach passengers that showed how their upper bodies were flung forward and then backward over the lap belts that kept them in their seats and undoubtedly saved their lives.

Manley said it was too early to determine if harness restraints would have prevented spinal injuries or simply moved the damage further up patient's backs. He hopes to study the issue.