Transportation Security Administration screening numbers are continuing to march closer to 2019 levels as the agency embarks on what’s expected to be a busy holiday season.Through Sunday, Nov. 21, November passenger screenings were at 83% of their month-to-date totals from 2019, and 228% of the totals from 2020. That’s an increase from October, when total screenings were at 79% of 2019 levels and 222% of 2020 levels.Want more airline-specific news? Sign up for TPG’s free new biweekly Aviation newsletter!Throughout the COVID-19 pandemic, TSA screening data has become a widely used metric to gauge the levels at which passengers are returning to the skies.Even before the holiday travel season began this past weekend, November was bound to be a busier month. On Nov. 8, the U.S. reopened its borders to international travelers from all countries, increasing the number of travelers going through TSA checkpoints as they return to their home countries.The TSA is expecting long lines at security checkpoints this holiday season. (Photo by Paul Hennessy/SOPA Images/LightRocket via Getty Images)The TSA expects to screen 20 million passengers during the Thanksgiving travel period, which for the agency runs between Friday, Nov. 19, and Sunday, Nov. 28. The agency’s busiest-ever day was the Sunday after Thanksgiving in 2019, when nearly 2.9 million passengers were screened. While the TSA does not expect to see that number this year, it is urging travelers to arrive at the airport early and to be patient.Sign up for our daily newsletterEmail addressSign upI would like to subscribe to The Points Guy newsletters and special email promotions. The Points Guy will not share or sell your email. See privacy policy.Additionally, United Airlines said last week that it expects to fly more than 4.5 million passengers during its Thanksgiving travel period (Nov. 19-30), which is approximately 88% of its 2019 volume. Delta Air Lines projects 5.6 million passengers during the same period, or nearly three times as many passengers as 2020.Enrolling in TSA PreCheck and joining Clear can significantly alleviate the headaches associated with long lines at TSA checkpoints.More: Why you should get TSA PreCheck and Clear — and how you can save on bothSeparately on Monday, the TSA announced that approximately 93% of its employees were in compliance with the Biden administration’s federal employee vaccination mandate, which has a deadline of today.“The employee vaccine mandate will not impact holiday travel,” agency spokeswoman Lisa Farbstein said in a tweet. Previously, there were some concerns that the vaccination mandate could cause a staffing shortage at the TSA.