U.S. transportation officials have slapped a $500,000 penalty on a South Korean airline, in connection with a crash last year in San Francisco that left three people dead and dozens injured.

Officials say Asiana Airlines failed to assist family members of passengers on that flight -- and that it took five days to reach the families of all 291 people on board.

Regulators say no airline had ever broken U.S. laws requiring prompt and generous assistance to the loved ones of crash victims.