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.

For the time being, passengers are able to fly either with a passport or by going through additional screening. Operations ran smoothly Wednesday morning.

The Real ID Act is now enforced by TSA at U.S. airports for domestic flights, prompting a rush to obtain compliant identification. At Philadelphia International Airport, travelers without a Real ID receive informational flyers from TSA.