Starting Wednesday, most U.S. travelers without a passport will be required to have a REAL ID to board domestic flights.After more than a decade of warning this day would come, the Transportation Security Administration says every flier over the age of 18 will be expected to have the security-enhanced REAL ID or an approved alternative to pass through airport security checkpoints.

Your domestic air travel could be delayed if you don’t have an accepted form of identification at TSA checkpoints come Wednesday, the deadline for “REAL ID.” After years of pushing it back, the Department of Homeland Security is set to enforce the May 7 deadline.