The National Transportation Safety Board said a series of slip-ups by pilots and air-traffic controllers twice put a US Airways Group Inc. jet and a Boeing 747 cargo plane on a near-collision course over Alaska last year.

Communication lapses by both sets of pilots, compounded by lax controller procedures, temporarily cut off radio contact between the relevant controller and the planes.

The board's report on the May incident, released earlier this week, indicates that the US Airways plane with 138 people aboard ended up flying 100 feet under the altitude of the Cargolux cargo jet. The planes were separated by less than one-third of a mile horizontally, as they maneuvered in good weather near the international airport in Anchorage, Alaska.

The report comes amid heightened concerns about reported controller errors nationwide, which have increased recently and last year prompted the Federal Aviation Administration to launch various safety initiatives. The safety board also has stepped up its scrutiny of midair near-collisions.

In the May incident, the US Airways Airbus A319 arriving from Phoenix encountered a wind shift and its crew decided to break off the landing approach and climb away from the airport. At the same time, the larger cargo plane was departing from a different runway. According to the safety board, misunderstandings between controllers and lax communication procedures by both cockpit crews resulted in the flight paths of the two planes converging twice during the incident.

The board found that the controller monitoring the A319's progress failed to keep proper track of its speed and direction, and didn't coordinate with another controller handling takeoffs and landings. The second controller tried but failed to contact the planes about the impending conflict, but both crews were tuned into another radio frequency.

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