Nearly two decades after Congress passed the Real ID Act, the law is finally set to be enforced.

Starting Wednesday, the Transportation Security Administration will begin checking for Real ID-compliant identification at airport checkpoints.

Homeland Security Secretary Kristi Noem told Congress on Tuesday that the government understands not everyone has been able to obtain a Real ID. Those travelers will still be allowed to fly but will be directed to a separate line for additional screening, she said.

Recent TSA data shows that only 80% of travelers have an acceptable form of ID.

How to tell if an ID is Real ID-compliant

Travelers can check the top of a driver's license or state-issued ID card. If it has a star, the ID meets federal Real ID requirements.

Other types of IDs that TSA will accept

• State-issued Enhanced Driver's License (EDL) or Enhanced ID (EID)
• U.S. passport
• U.S. passport card
• DHS trusted traveler cards (Global Entry, NEXUS, SENTRI, FAST)
• U.S. Department of Defense ID, including IDs issued to dependents
• Permanent resident card
• Border crossing card
• An acceptable photo ID issued by a federally recognized Tribal Nation/Indian Tribe, including Enhanced Tribal Cards (ETCs).
• HSPD-12 PIV card
• Foreign government-issued passport
• Canadian provincial driver's license or Indian and Northern Affairs Canada card
• Transportation worker identification credential
• U.S. Citizenship and Immigration Services Employment Authorization Card (I-766)
• U.S. Merchant Mariner Credential
• Veteran Health Identification Card (VHIC)

What about children?

Children under 18 are not required to show identification when traveling domestically, according to the TSA.