DENVER -- The United Airlines pilot who is accused of misusing a Social Security number to obtain access to restricted areas of Denver International Airport turned himself into authorities Thursday morning.

Joseph Maxwell Raulins, 59, voluntarily surrendered to the U.S. Marshal Service to face a charge that came about during the recent DIA raid, known as Operation Safe Sky.

The operation was conducted as part of a national effort that began after the terrorist attacks to crack down on workers who fraudulently obtained access to restricted areas of the country's airports.

Authorities say terrorism is one of several motives that would lead a person to use a phony Social Security card, although none of the 110 airport workers named during Tuesday's operation are suspected of terrorist-related crimes.

Officials also say offenders could be hiding criminal records or problems with child support or they could be trying to conceal their citizenship, or lack thereof.

Federal prosecutors speculated that Raulins was trying to hide his felony arrest earlier this year to obtain a security pass.

Raulins was charged in May with two counts of sexual assault on a child when two girls reported that they had been inappropriately touched while shopping at a Highlands Ranch Target store.

Raulins made an initial appearance at a U.S. District court Thursday afternoon. Prosecutors want him detained, believing he is a flight risk.

His arraignment and detention hearing is scheduled for Tuesday, Sept. 24.

If convicted, he faces up to five years in federal prison, a $250,000 fine, or both.