(CNN) — Think your driver's license is enough to get you through US airport security and onto your domestic flight?

Better make sure soon.

On October 1, 2020, travelers will need a "REAL ID-compliant" driver's license, US passport, US military ID or other accepted identification to fly within the United States.

The REAL ID Act established minimum security standards for the issuing of state licenses and their production.

It also prohibits federal agencies from accepting licenses from states not meeting those minimum standards for certain activities. That includes boarding federally regulated commercial aircraft, entering nuclear power plants and entering federal facilities.

To get a REAL ID-compliant state driver's license, the US Department of Homeland Security requires applicants provide documentation showing their full legal name, their date of birth, their Social Security Number, two proofs of address of principal residence and lawful status. (States may impose more requirements.)

Todd Hauptli, CEO of the American Association of Airport Executives, shows his REAL ID-compliant driver's license during a news conference at Ronald Reagan Washington National Airport on October 1, 2019. Manuel Balce Ceneta/AP

No REAL ID, no clearing security

If you can't produce acceptable identification, your US airport's Transportation Security Administration (TSA) checkpoint will not clear you for flight.

That could lead to serious backups at US airports starting October 1 of next year.

"We have real concerns, based on some recent surveys we did, that 99 million Americans do not have any form of REAL ID-compliant identification," said Tori Emerson Barnes, executive vice president of public affairs and policy at the U.S. Travel Association , a national, non-profit industry organization.

Which leads to another concern: Over half of Americans (57%) have no idea this deadline is coming, said Barnes, according to a recent U.S. Travel survey.

Related content The TSA race to the gate

The Department of Homeland Security reported Tuesday that 47 out of 50 states are currently REAL ID compliant, up from January of 2017, when only 26 states were REAL ID compliant.

Those slow-to-adopt states -- New Jersey Oklahoma and Oregon -- aren't yet issuing REAL ID-compliant cards. In Pennsylvania , REAL ID-compliant documents are available, but not required, which can lead to confusion.

And while most states offer more secure identification, only 27% of Americans have been issued a REAL ID, according to the Department of Homeland Security.

Many states have been issuing compliant documents for years, but driver's licenses and other documents issued before the adoption of REAL ID standards don't meet the requirements.

The easiest way to check if your state driver's license or identification card is REAL ID compliant is to see if there's a star in the upper right hand corner. Some state departments of motor vehicles will confirm REAL ID status online.

A post-9/11 security measure

A passenger enters the TSA PreCheck line at an airport security checkpoint. Bloomberg/Getty Images

Passed by Congress in 2005, the REAL ID Act's requirements have been delayed for years, despite being included in the 9/11 Commission's recommendation that the federal government set standards for the issuance of sources of identification, according to the Department of Homeland Security.

Since the act's 2005 passage, the federal government has implemented TSA Pre-Check and other programs that offer more security than REAL ID, says Barnes. That's why the U.S. Travel Association is talking with federal authorities to see if they'll consider membership in those programs as a substitute for REAL ID.

It's a real concern to U.S. Travel, which represents major airlines, hotels, state and local tourism boards and other travel industry members that could lose customers who suddenly can't fly within the United States starting October 1, 2020.

What qualifies as REAL ID

A US passport qualifies as a REAL ID. Jeff Haynes/AFP/Getty Images

• REAL ID-compliant state driver's licenses or other state photo identity cards

• US passport

• US passport card

• DHS trusted traveler cards (Global Entry, NEXUS, SENTRI, FAST)

• US Department of Defense ID, including IDs issued to dependents

• Permanent resident card

• Border crossing card

• State-issued Enhanced Driver's License

• Federally recognized, tribal-issued photo ID

• HSPD-12 PIV card

• Foreign government-issued passport

• Canadian provincial driver's license or Indian and Northern Affairs Canada card

• Transportation worker identification credential

• US Citizenship and Immigration Services Employment Authorization Card (I-766)