However, they might be able to take a bus or train instead.

The Transportation Security Administration is supporting a provision of Utah law prohibiting the new driving cards from being used as a valid form of identification at any state government agency, said Earl Morris, federal security director for the state's TSA office.

"We will respect the state's intent for the usage of that card and that was clearly for driving privileges," he said. "The card's intent was not to be used as a form of identification."

To get on a flight in the United States, a person must show an official identification card with a photo issued by any state or country government, Morris said. For example, an ID card, driver license or passport, from anywhere from Mexico to Poland, he said.

The new Utah law only allows a person with a Social Security card to get a state identification card or driver license, forcing some residents, many of them undocumented immigrants, to apply for a driving privilege card. But the card is not a valid form of ID at any government agency, though some banks and auto insurance agents are accepting it.

A recent legislative audit showed that Utah issued roughly 19,000 driver licenses or ID cards a year to undocumented residents since 1999. Utah is one of a handful of states that give undocumented people legal driving rights.

About 900 driving cards have been issued since the legislation was signed into law on March 8, said Derek Jensen, a state Department of Public Safety spokesman.

Morris said he hopes the driving card issue doesn't keep Utahns from using airports, adding "This is not to discourage people from flying."

People who only show a driving card will not be allowed on their flight, but some airlines might allow them to board if they pass additional security tests, Morris said. Airlines have the option to designate travelers as "selectees," who are screened twice by security.

"The screening process is what makes you a safe passenger," Morris said.

Salt Lake City International Airport is used by 17 airlines, said spokeswoman Barbara Gann. Of the airport's scheduled 954 daily flights, about 70 percent are by Delta Air Lines, she said.

Since the airport doesn't track what ID cards are used by travelers, "there's just no way we will know how many passengers this will affect," Gann said.

But Anthony Black, a Delta spokesman based in Atlanta, said the airline will comply with TSA regulations and Utah law by not allowing people showing only a driving card to get on a flight. Delta will not designate people as "selectees" to fly, he said.

"If the government said this form of identification is not valid, it's not valid," Black said of the driving cards.

Southwest Airlines Co. spokeswoman Marilee McInnis said the Dallas-based company would comply with TSA regulations, but she did not immediately know if Southwest would allow "selectees" on its flights.

Morris said TSA does regulate ground modes of transportation, but there has been no decision on whether driving cards will be accepted by train or bus lines.

Until then, Amtrak will accept the driving card as a form of identification, said Sarah Swain, a company spokeswoman in Oakland, Calif. She said as long as travelers show a government-issued ID, they can get on a train.

Greyhound Lines also will accept the driving cards to get on a bus, said Kim Plaskett, a company spokeswoman in Dallas.

jsanchez@sltrib.com