The time has come. Starting Wednesday, passengers nationwide must use a state-issued ID or license that is “REAL ID” compliant to travel within the US.

Aside from being used to board domestic flights, the identity cards are also federally complaint and are used 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.

“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 there are other forms of identification travelers can show ahead of flying.

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

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, which enacted the 9/11 Commission’s recommendation that the federal government enhance security standards for identification, 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 delays and cancellations at Newark Airport.

The TSA on Tuesday reminded travelers that enforcement of REAL ID starts 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.

Some airports will also have separate lines for people who do not have Real IDs, or other documentation.

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).”

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.

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.

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 contributed to this report.