US aviation chiefs are no longer allowing foreign airlines to land alongside another plane when touching down at San Francisco International Airport.
The Federal Aviation Administration said it made the change to minimise distractions during a critical phase of flight.
The move comes in the aftermath of the Asiana Airlines crash, and on the same day the FAA started advising foreign airlines to use a GPS system instead of visual reckonings when landing at San Francisco.
In the past, two planes could approach the airport side by side if the weather was clear. Domestic carriers can do that, but air traffic controllers are now staggering the arrivals of foreign carriers.
FAA spokesman Ian Gregor said the agency had not seen any significant delays as a result of the change.