Drivers with valid D.C. licenses could one day find themselves turned away at the airport ticket counter or security lines while the city's Department of Motor Vehicles simultaneously faces a bureaucratic nightmare, if proposals floated by D.C. Council members become law.

At least that's what the mayor's office warns could come to pass if the D.C. Council has its way and strips the Social Security requirement for getting a driver's license in the District.

Mayor Vincent Gray and Council Chairman Phil Mendelson have two competing proposals that would allow the District's undocumented immigrants to earn D.C. driver's licenses. The two bills were debated Thursday during a sometimes emotional council hearing.

Gray has thrown his support behind a plan that would allow illegal immigrants residing in the District to get a D.C. driver's license with a label indicating that the license is not meant to be used for federal identification.

The Gray administration believes that strategy will keep the District in line with federal requirements, ensuring that standard-issue D.C. driver's licenses remain an acceptable form of federal identification.

Otherwise, the executive branch worries that D.C. drivers wouldn't be allowed to use their driver's licenses to board an airplane or to enter a federal building.

"Something has to be marked so the residents do, in fact ... have something to board a plane," Lucinda Babers, director of the Department of Motor Vehicles, said during Thursday's hearing. "We've got to give [the federal government] something to know which one are they looking at."

But many council members -- and a vocal chorus of immigrants and advocates -- believe that two-tiered system is discriminatory.

"We believe this sort of marked license will open the door for discrimination," said Joslyn Williams, president of Metropolitan Washington Council AFL-CIO. "We are one city, and we need one standard license."

One competing bill, drafted by Mendelson and Ward 1 Councilman Jim Graham, would allow District residents to get a driver's license without a Social Security number, making it possible for illegal immigrants to get a driver's license without needing to prove U.S. citizenship.

Council members floated other alternatives to the mayor's bill Thursday, as well.

Mary Cheh, chairwoman of the Committee on Transportation and the Environment, suggested creating a driver's license for all D.C. residents and then a separate identification card for federal purposes.

Meanwhile, at-large Councilman David Grosso opposed creating a federal identification card at all.

"I'd rather not have a real ID. We already have one: your passport," Grosso said.