Canadian aviation officials, back from a tour of the air traffic control center in Leesburg, said yesterday in Ottawa that the U.S. control system is operating "in a professional and safe manner," a Canadian government statement said.

The head of the Canadian controllers' union, which last month crippled transatlantic aviation with a two-day boycott of flights to and from the United States, immediately dismissed the claim as a gesture of "solidarity" with the U.S. government.

To test the system first-hand, the Canadian government team flew to Washington Tuesday in a plane piloted by a Canadian air traffic official, a government spokesman in Ottawa said. The pilot said that the control network is "working as well as it ever has, if not better."

During their one-day visit, the Canadians met with Federal Aviation Administration chief Lynn Helms and interviewed controllers and supervisors at the air control center at Leesburg, which directs air traffic through a 140,000-square-mile area around Washington.

Canadian Air Administrator Walter McLeish praised U.S. preparation for the strike. He said it had allowed 75 percent of commercial flights to continue operating "with no reduction in safety." He dismissed allegations of violations made by controllers' unions.

Bill Robertson, president of the Canadian Air Traffic Controllers Association, yesterday rejected the team's statements. While publicly labeling the U.S. system safe, he said, the government has privately instructed controllers to take extra precautions with U.S. traffic.

Robertson read from what he said was a memo from the chief of the Calgary control facility in western Canada to staff members there. It advised that there was evidence of "some degree of degradation in accuracy" in flight data coming from U.S. facilities at Salt Lake City and Seattle and outlined special procedures to take with planes crossing the border.

Robertson also pointed out that the Leesburg facility, which the Canadian team visited, has nothing to do with his union's concerns over cross-border traffic. Leesburg lost only about 40 percent of its controllers to the strike, compared to 75 percent nationwide.

According to the union president and the Canadian government spokesman, the FAA had cleared Robertson for the U.S. trip but withdrew the invitation because of his criticism of the U.S. system. But yesterday FAA spokesman Gerald Lavey said Robertson had never been invited on the trip.

The Canadian union called off its boycott last month in return for a joint government-union investigation of reported safety violations on cross-border routes.

So far joint teams have investigated more than 40 reported incidents, with both sides claiming that the findings prove their contentions. In incidents where procedural errors were confirmed, none of the planes involved were found to have actually violated separation rules as a result. However, in most cases where procedural errors were made, they were made by U.S. air traffic controllers.