Now that the Transportation Security Administration's Pre-Check program is open for application to any American, its reach is growing quickly: Eight airport enrollment centers have opened nationally since November, and at least 40 more are expected by the end of the year.

The application process for expedited airport screening is relatively simple, requiring just some biographical information, an $85 fee and a set of fingerprints.

It was the fingerprints that gave me pause.

Charles Carroll, senior vice president for identity services at MorphoTrust USA, the firm contracting with the TSA to operate the enrollment centers, said his company's job is to "collect fingerprints and biographical information in a secure way and transmit it to the FBI."

"The FBI does the background search and makes sure the fingerprint belongs to who someone says they are," Carroll said.

But what happens to the fingerprints when the FBI is finished with them?

Carroll didn't know. So I called the FBI.

Steve Fischer, a spokesman for the FBI's Criminal Justice Information Services Division, said the prints are compared to a database called the Integrated Automated Fingerprint Identification System, which includes the prints of 76 million people. Most were collected at the time of arrest or conviction from about 18,000 law enforcement agencies, Fischer said.

If someone applying for Pre-Check matches up in the database, the FBI passes on word to the TSA, and (presumably) the applicant is denied.

But what happens to the fingerprints? And is it worth volunteering your prints simply to enjoy expedited airport screening? Fischer said there's no reason to worry: The FBI doesn't keep the prints, because it is not legally entitled.

"We're not authorized to keep those prints," he said. "We either send them back or destroy them."

Carroll said MorphoTrust also does not keep copies of the prints.

I might not have a practical reason to care about the FBI having my fingerprints — I have no plans to commit major crimes — but I doubt I'm alone with my unease about being biologically cataloged by my government. And, as recent Edward Snowden-related revelations have shown, it's naive to assume the government will opt for the least invasive approach.

So I called the American Civil Liberties Union for its take. Jay Stanley, an ACLU senior policy analyst, said he takes the FBI at its word.

"If they say that, I believe them that they're not using this as an enrollment" into the fingerprint database, Stanley said. "And I think that's good."

That said, Stanley said he won't be enrolling in Pre-Check, a program he has previously criticized in this space for creating a tiered system of airport security. (The TSA has argued that it is creating a more efficient system by targeting travelers it knows less about, rather than using a one-size-fits-all approach.)

"I don't believe in it," Stanley said. "I think it's the wrong direction to go down the road of categorizing Americans of who is trustworthy and who isn't."

jbnoel@tribune.com