The International Association of Machinists has filed a federal lawsuit accusing US Airways of using bankruptcy law to avoid an arbitration case stemming from a union grievance.

US Airways Group Inc. last week filed a complaint against the union, which represents airline mechanics and baggage handlers, asking U.S. Bankruptcy Court in Alexandria, Va., to block an arbitration hearing that was scheduled to start Monday.

The union lawsuit, filed Monday in U.S. District Court in Alexandria, asserts that US Airways should not be allowed to use the Bankruptcy Court to shield itself from its obligations under the Railway Labor Act to resolve collective-bargaining disputes. US Airways spent just over a year in Bankruptcy Court protection before emerging Sept. 27, 2005, when it merged with America West Holdings Corp.

The union said its agreements with the airline provided for automatic wage adjustments upon a change in control of the airline. The labor group filed its grievance in October 2005.

"If companies can get Bankruptcy Court protection without filing for bankruptcy, no business contract, labor or otherwise, is enforceable," Robert Roach Jr., the union's general vice president, said in the statement. "Lessors, vendors, bondholders, stockholders and other creditors are also at risk."

In a statement yesterday, US Airways spokesman Philip Gee said the company had been prepared to arbitrate the dispute, but, after researching the issue, determined "that this properly belonged in the Bankruptcy Court. That's when we filed our petition with the Bankruptcy Court, prompting the IAM's actions."

Contact staff writer Tom Belden at 215-854-2454 or tbelden@phillynews.com.