The time has come. Travelers flying within the US starting Wednesday must use a state-issued ID that is “REAL ID compliant” or be subject to further screening.

Things seemed to be operating relatively smoothly at a sampling of US airports early Wednesday. Signs about the REAL ID requirements are posted, and TSA representatives at some airports were ushering people without REAL IDs to separate lines for enhanced screening.

Lines outside some states’ departments of motor vehicles may be a different story, however, as people who haven’t received a compliant ID try to catch up. In downtown Chicago, for example, a line Wednesday morning to get into a walk-in “supercenter” dedicated to issuing REAL IDs wrapped around a city block.

REAL IDs, aside from being used to board domestic flights, also will be required to enter secure federal facilities. REAL IDs are marked with a star in the upper right-hand corner, no matter what state you live in. The 9/11 Commission recommended the new standard for enhanced security.

“State-issued driver’s licenses and IDs that are not REAL ID compliant are no longer accepted as valid forms of identification at airports,” the Transportation Security Administration explained. However, if passengers show up Wednesday without a REAL ID, they will still be able to fly but “may” face additional screening, officials said this week. And air travelers can show alternative forms of ID, including a passport, a Veteran Health Identification Card, and other items.

How things are going at the airports

At Philadelphia International Airport Wednesday morning, the REAL ID implementation went smoother than even some federal officials were expecting.

“The traveling public was great, they responded, they were prepared, everything went as well as it could be expected,” said Gerardo Spero, TSA federal security director for Pennsylvania and Delaware.

Security lines at the airport moved quickly, with relatively few passengers diverted for additional screening because they did not have a REAL ID. Many passengers opted to use their passports – an acceptable alternative for flights – as their ID.

“I don’t think we’ve ever seen quite as many passports, certainly not for domestic flights,” Spero said.

At Atlanta’s Hartsfield-Jackson International Airport, the world’s busiest airport, officials initially had a separate security lane Wednesday morning for those without a REAL ID. But that extra line was eliminated mid-morning because so few travelers were without one – and TSA officers will now do additional screenings as needed after passengers arrive at regular document checkpoints, airport lead transportation security officer Alexis Pickerel said.

And at North Carolina’s Charlotte Douglas International Airport, staff were prepped with more security lanes than usual and additional staff to help travelers at the REAL ID deadline – but for the most part, travelers had the identification they needed and moved smoothly through security, a CNN crew saw.

The relative order at airports may depend on the state and how many residents obtained REAL IDs ahead of Wednesday’s deadline. Georgia and Florida, for example, say more than 99% of their residents’ driver’s licenses or ID cards are REAL ID compliant.

Alabama, however, had only 33% REAL ID compliance, Alabama Law Enforcement Agency Capt. Jeremy Burkett said. North Carolina’s REAL ID compliance, meanwhile, was at 52%, state transportation department spokesperson John Brockwell said.

Nationwide, the Department of Homeland Security put it this way in a Wednesday news release: “Most travelers won’t even notice a difference because 81% of travelers are already REAL ID compliant.”

Here’s what to expect if you’re flying after Wednesday’s deadline.

Can I fly after Wednesday if I don’t have a REAL ID?

Wednesday is not the deadline for obtaining a REAL ID — it’s just the date the new requirement for air travel goes into effect. People can still get a REAL ID after May 7.

Additionally, passengers without one will not be turned away at airports, Steve Lorincz, TSA’s deputy executive assistant administrator for security operations, told CNN.

“We will process you (and you) will not be turned away,” Lorincz said. “It might take some additional time, but we’re going to do it efficiently. We are fully staffed at all locations across the country.”

Wednesday’s deadline to enforce the 2005 REAL ID act was pushed back several times.

The 20-year-old law requires state drivers’ licenses to meet certain federal requirements to be used for boarding a plane or accessing federal facilities requiring identification, but about 19% percent of people flying nationwide do not have them yet, the TSA says.

The deadline left many confused travelers scrambling to comply ahead of holidays and the summer months.

The enforcement is now happening amid flight delays and cancellations at Newark Airport, a key hub in New Jersey that serves the busy New York area.

‘Be prepared’

The TSA on Tuesday reminded travelers that enforcement of REAL ID was to start Wednesday. Those without one may be subject to additional screening, and that includes TSA Pre-Check passengers.

“Plan ahead, arrive early, and arrive prepared,” the agency said in a post on X.

Travelers can find if they are “REAL ID ready” by using the TSA’s interactive tool.

“We’ll have staff in front of all our checkpoints to help and direct our customers as they transit through the security process,” Lorincz said.

The agency will work with states, airlines and airports toward an eventual time where enough people are showing up at airports with the correct ID, a TSA spokesperson told CNN.

“The bottom line is, if you don’t have an acceptable form of ID such as a passport or a REAL ID, give yourself plenty of time when you arrive to ensure you can get through everything from the curb to the gate,” the spokesperson said. “We’re definitely implementing REAL ID … but nobody’s going to be turned away (Wednesday).”

What is still accepted at TSA checkpoints?

Adults 18 and over must show valid identification at airport checkpoints to travel.

Other forms of identification that will still be accepted at TSA checkpoints include a US passport or passport card, a permanent resident card, a border crossing card and a Veteran Health Identification Card, among others.

Those who do not have a valid form of identification may be asked to complete an identity verification. Once a traveler’s identity is confirmed, they will be allowed to enter the checkpoint where they may be subject to additional screening, the TSA says.

What states are doing

Required documentation and the cost of the ID varies from state to state and each has its own system for issuing them. The TSA links to each state’s department of motor vehicles to explain what residents may need to get one.

“DMVs are working really, really hard to make sure that we’re getting people in so they can get their REAL IDs as we continue to move forward,” Lorincz said.

But lines at some DMVs have been long, potentially discouraging people from staying and getting the ID. In North Carolina, Elena Campbell had made several visits to her DMV to try to get a REAL ID, only to leave because of long wait times, she told CNN Tuesday on her fourth visit.

“They don’t make it easy on you,” she said. “We’re just out here doing what we’re supposed to do.”

In preparation for the transition, California’s Department of Motor Vehicles is offering extended hours and Saturday appointments to residents looking to get a REAL ID.

The New York State Department of Motor Vehicles indicates on its website that officials are seeing “an increased volume” in offices due to the REAL ID implementation.

“It’s time to get your REAL ID. No, really,” the Service Oklahoma website reads.

It reminds residents who are traveling soon to apply for a REAL ID at least four weeks early because the TSA “won’t accept a temporary paper ID,” and that IDs are mailed within one to two weeks after a visit.

CNN’s Alexandra Skores, Lauren Mascarenhas, Whitney Wild, Jason Morris, Dianne Gallagher and Maxime Tamsett contributed to this report.