Prosecutors claim Micheline Johnson, 49, of Concord, skimmed customers' credit card numbers for several years while she worked as a customer service agent.
They say she used those numbers on counterfeit credit cards to make purchases of more than $480,000 at Safeway stores in California, Nevada and Washington.
The alleged scheme began sometime around December 2007 and lasted through October 2010, Deputy District Attorney Tom Flattery said.
Safeway analysts allegedly linked Johnson to at least 2,800 transactions using 350 credit card numbers. Several victims claimed their accounts were used at other retailers as well.
Johnson is being held at Santa Clara County's main jail on $1 million bail.
She will enter pleas on charges of grand theft, possession of stolen property, and identity theft on Feb. 28.
Flattery said Johnson had been an American Airlines employee for 20 years.
If convicted, Johnson could face up to 48 years and 4 months in prison.
The case was investigated by REACT, a Santa Clara County District Attorney's Office-led high-tech crimes and identity theft task force.