The Federal Aviation Administration said no standard rules existed for "opposite-direction" operations used at airports nationwide. Such switches are made for noise mitigation and cargo operations among other things.

They occur when an arrival or a departure is cleared to use a runway end that is opposite from the established flow of traffic.

In the July 31 incident over Reagan National, two regional commuter jets took off in the direction of an incoming flight with inadequate separation.

The mishap was caused by "miscommunication" between the control tower and a regional traffic-control hub while reversing traffic flow because of bad weather developing to the south, according to FAA preliminary findings.

The FAA believes the lack of a standard protocol for opposite-direction operations contributed to the miscommunication, J. David Grizzle, the FAA's chief operating officer, said in a memo.

This was the case even though such a switch involves many of the same elements as turning the flow of an airport overall, a routine manoeuvre, said the FAA, the Transportation Department arm responsible for operating the nation's air-traffic control system.

The FAA, as a result, has suspended opposite-direction operations at commercial airports until detailed procedures can be developed and implemented through training "out of an abundance of caution," he said.

Standard procedures are expected to be in place across the air-traffic control systems within a month and sooner at locations that need to use them frequently, Grizzle said.

The too-close flights near Washington were the latest in a string of incidents that highlight concerns over air traffic safety.

Grizzle said preliminary findings showed that the aircraft over Reagan were never on a head-to-head course and they remained at different altitudes.

The FAA has concluded that managers' intentions at the regional traffic-control hub had been to turn only a series of arrivals, he said.

"Only after the loss-of-separation events was the flow of traffic at the airport turned completely," Grizzle said.

Standard separation distances -- 1,000 feet vertically and three nautical miles laterally -- were breached over Reagan when one of the inbound flights came as close as 800 feet vertically and .82 miles laterally of an outbound flight.

(Reporting By Jim Wolf; editing by Sofina Mirza-Reid)

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