Updated from 1:41 p.m. EST

The management of

US Airways

(U) - Get Report

and its flight attendants union made a last-ditch effort Friday to resolve a contract dispute and prevent the airline from shutting down.

As of Friday, 16 out of the 32 clauses in the flight attendants' contract were still in dispute, including issues of pay, training and scheduling, said Steve Hearn, an official with the

Association of Flight Attendants

and a US Airways flight attendant.

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If the two sides fail to reach an agreement by midnight, US Airways will impose a shutdown as of 12:01 a.m. on Saturday morning in order to prevent the flight attendants from embarking on a random strike plan that would interrupt service at certain unspecified hubs throughout the nation.

Richard Weintraub, a US Airways spokesman, said the airline decided it would shut down "rather than subject our customers to that type of uncertainty."

The airline did, however, say in a statement on its 1800-USDAILY hotline that it was committed to reaching an agreement before the midnight deadline and that it had offered alternative ways for achieving wages that would be competitive with the four leading airlines.

Wall Street reacted nervously Friday to the possibility of a strike. US Airways' shares fell 1 1/16, or 4.5%, to close at 22 3/8.

The flight attendants union maintains that the airline's method for calculating the wages, a formula known as "parity plus 1%," is actually based on the way pilots clock their hours rather than the way the flight attendants clock theirs.

"The problem we've had with the parity concept is that the company is not using a formula built on what we do as flight attendants," Hearn said, noting that the disagreement has been going on for three years. "We need our own formula."

Brian Harris, an analyst at

Salomon Smith Barney

, said in a report that a shutdown would trim US Airways' pre-tax earnings by $10 million to $15 million a day, or 10 to 12 cents a share. Harris rates US Airways a neutral and his firm has done no underwriting for the airline.