US Dept. of Homeland Security is scrambling to avoid a potentially chaotic scenario in which driver's licenses issued by three and possibly four states would become legally unacceptable for presentation as airport identification beginning May 11.

A US law enacted in 2005 compels states to issue licenses -- the primary form of identification used by US citizens -- with multiple federally approved security features. While the deadline for first-phase compliance is May 11, DHS has issued numerous extensions to states that have demonstrated they are progressing toward issuing approved licenses in the next few years. But the deadline for applying for an extension is March 31 and Maine, Montana and South Carolina have yet to do so. It also is unclear whether New Hampshire properly sought one.

The non-complying states insist their licenses are secure and complain that making the required changes would be unnecessarily costly. Montana Gov. Brian Schweitzer (D) called the federal law a "boondoggle" and South Carolina Gov. Mark Sanford (R) said he may file a lawsuit against DHS.

In a letter to US senators representing the four states in question, DHS Secretary Michael Chertoff warned that "showing up at the airport [after May 11] with only a driver's license from such a state will be no better than showing up without identification." Passengers would be able to use passports, but fewer than 30% of Americans are believed to have passports and even those who do are unaccustomed to carrying them for domestic travel.

On March 24, Airports Council International-North America Senior VP-Security and Facilitation Charles Chambers told reporters in Washington that DHS took the unusual step of holding a conference call with a range of airport and airline officials last week. "It's clear that this was of high priority," he said. While airports pressed for a written statement from DHS outlining how the situation would be handled should the four states remain non-compliant, the department issued only a "verbal statement" of its plans, he said.

According to Chambers, Transportation Security Administration screeners will be forced to conduct "secondary-screening" checks on all passengers with licenses from the states, meaning full "pat-downs" that officials at more than one dozen commercial airports in the four states fear may create significant congestion and airports in other states worry could lead to confusion.