A review of maintenance records showed a test of the fire- suppression system on its 777s hadn't been performed, the Chicago-based airline said in a statement today. The equipment is now being scrutinized and the U.S. Federal Aviation Administration has been informed.

``United will not operate these aircraft until the tests are complete,'' the company said. The airline said it's working to provide additional planes or accommodate passengers with other carriers. Customers should check the status of their flights before leaving for the airport, it said.

United is one of at least four major U.S. carriers whose maintenance regimes are under scrutiny after it said this week that crossed landing-gear wires may have caused two Airbus SAS A320 jets to skid off runways. Regulators last month proposed a $10.2 million fine for Southwest Airlines Co. over missed inspections and American Airlines and Delta Air Lines Inc. last week grounded jets while complying with a government directive.

The maintenance gap concerned the failure to perform a test on the firing mechanism on one of five bottles in the cargo fire suppression system of the 777s, United said today.

Customers can check which aircraft they are scheduled to fly on at united.com, the company said.

Source: Bloomberg