United States – Do I need a passport for domestic flights in the United States, due to the requirements of REAL ID 2019?

March 24, 2020 update:

To reduce the need for people to go to the offices of the DMV during the coronavirus pandemic, the October 1, 2020 deadline has been extended. No new date has yet been determined. Thanks to Choster for linking to a Bloomberg News report.

Take a look at https://www.dhs.gov/real-id-public-faqs:

As of January 22, 2018, passengers who have a driver's license issued by a state that is not yet REAL ID compliant and that has not received an extension will have to show another form of identification acceptable for air travel. Please see the TSA website for a list of acceptable forms of identification. Passengers who have licenses issued by a state that is compliant or that has an extension to comply with REAL ID requirements can continue to use their licenses as usual. For a list of states already in compliance or with an extension, visit the DHS REAL ID web page. DHS continually updates this list as more states become compliant or obtain extensions.

As of October 1, 2020, each resident of the state and territory must present a REAL ID compliant license / ID, or other acceptable form of identification, to access federal facilities, enter nuclear power plants and board commercial aircraft. This is what we call a "card-based" application. The card itself must conform to the TRUE ID, unless the resident uses another acceptable document such as a passport. The law does not require individuals to present identification when they are not currently required to access a federal institution (such as entering public areas of the Smithsonian) nor does not prohibit an organization from accepting other forms of identity documents other than non-compliant non-state documents (such as a US passport or passport card).

Yes Pennsylvania complies (or has an extension), so you can use a document issued by Pennsylvania (license or ID card), even if the document is not compliant until September 30, 2020. After that, you would need a document that is compliant or issued by the federal government (for example, a passport or passport card).

Is Pennsylvania Compliant? Does it have an extension? See the main Real ID page at https://www.dhs.gov/real-id, which shows a map showing that Pennsylvania has an extension. You can choose Pennsylvania in the "select a state" box under the map to see details:

Pennsylvania has an extension for the application of TRUE ID, allowing federal agencies to accept Pennsylvania driver's licenses and identity cards at federal facilities, nuclear power plants and aircraft federally regulated sales representatives until August 1, 2019.

If you are traveling between August 1, 2019 and September 30, 2020, then you will want to check this page again and decide to bring your passport based on what you will find. Or you can just upgrade to a Real ID license now if you prefer, and not have to worry about it all.

After October 1, 2020, you will need a Real-ID-compliant driver's license or your passport (or another document from the ASD list, if you have one).