A former employee at Langley Air Force Base admitted Wednesday that she conned the federal government out of $1.46 million — mainly by faking the amount of overtime she worked over 17 years.

Michelle M. Holt, 52, was a civilian secretary at the base, where she worked in the communications support squadron of Air Combat Command.

She pleaded guilty in U.S. District Court in Newport News to felony charges that she undertook a long-running effort to boost her own pay.

According to court documents Michelle M. Holt, 52, was previously employed as a federal employee for the Department of Defense. Holt worked as a secretary for U.S. Air Force at Joint Base Langley-Eustis. In that capacity, Holt was a salaried employee on the General Schedule (GS) grade for the federal civilian workforce and was entitled to overtime pay if authorized by her employer, and also to other forms of holiday and annual leave, as well as premium pay for any federal holidays worked.

A law enforcement investigation determined that from December 2001 to July 2018, Holt falsely claimed over 42,000 hours in unauthorized overtime that she did not work, as well as other amounts of unauthorized holiday leave, sick leave and annual leave, all amounting to losses to the United States of $1,460.262.43. In recent years, Holt’s overtime pay was over double that of her regular salary.  She accomplished the fraud by making manual retroactive adjustments to protected computer time and attendance systems to add overtime, reverse leave taken and reverse holiday leave.

It began in late 2001, when Holt used a co-worker’s log-in information — without that co-worker’s knowledge — to get into a Department of Defense computerized pay database. She retroactively added 15 hours of overtime to her paycheck.

As time went on, Holt’s retroactive additions to her overtime “became a regular occurrence,” the statement said. She began to get bolder, particularly after 2008 — when her overtime pay began to double her regular salary.

In 2017, for example, Holt’s salary was $51,324. But she took home $119,585 in overtime pay.

In one two-week period, the statement said, she billed the Air Force for 137 overtime hours that she didn’t work.

But things began to unravel in June, when the Department of Defense’s Inspector General’s Office found discrepancies between Holt’s pay and attendance records.

She appeared to get wind that an investigation was afoot. Holt wrote to a co-worker on June 18: “Please keep this between us, have you all had (the Air Force’s Office of Special Investigations) come over here about anything?”

She first told investigators she took extra overtime for only a few months. But an investigator then showed Holt a spreadsheet of her overtime going back 10 years. “I’m in trouble,” she said, according to the statement of facts. “It was wrong.”

In Wednesday’s plea agreement, Holt admitted to both charges she faced — computer fraud and theft of government property. When she is sentenced March 13 by U.S. District Judge Raymond Jackson, she faces up to 15 years in prison, plus fines and forfeitures.

In the plea agreement, prosecutors promised to ask Jackson to give Holt credit for cooperating with them.

“The defendant has assisted the government in the investigation … by timely notifying authorities of (her) intention to enter a plea of guilty, thereby permitting the government to avoid preparing for trial,” the plea agreement said.

“She was a long-term employee at Langley, and she took her job very seriously,” said her lawyer, William Johnson. “She loved what she did … and she’s very emotional about it.”

“New employees would come to her” for advice on getting acclimated to the Air Force and how things worked at the base, said Holt’s other attorney, Amy Van Fossen.

Holt spent the money on “life and paying daily bills” rather than on spending on luxury items, Johnson said. “There were no exorbitant expenses,” he said.

Holt will be sentenced on March 13.