Australia to Limit Flights by Northwest : Aviation: Restrictions will take effect at the end of June. The U.S. has threatened to retaliate against Qantas Airways.

The Australian government said Tuesday that it will restrict Northwest Airlines flights as of the end of June, despite U.S. threats of retaliation against Qantas Airways.

Three weekly Northwest flights to Sydney will be canceled, but Northwest can reapply for two flights to be reinstated, Transport and Communications Minister Bob Collins said.

Northwest now originates the flights in New York with a stop in Osaka, Japan, before heading to Sydney.

For almost two years, Northwest has not met an Australian demand that no more than half the Sydney-bound passengers originate in Osaka. The other half must board in New York.

The airline says the rule unfairly limits its Japanese operations and violates the U.S.-Australian aviation treaty.

“We consider this a very serious matter,” said Doug Killian, director of international communications for Northwest. “We have contacted the U.S. government to take appropriate action against Qantas.”

Australia ordered Northwest to comply last December. The government first threatened restrictions in April when arbitration with the airline failed.

Last week, U.S. authorities ruled that Qantas will be required to cut its services between Sydney and Los Angeles by three weekly nonstop flights if the restrictions went ahead.

Qantas now operates 18 weekly round-trip flights between Sydney and Los Angeles, 10 of them nonstop.

A U.S. Department of Transporation spokesman in Washington said the government will go through with its threatened retaliation if Australia cancels the Northwest flights at the end of June.