The Transportation Security Administration screened 2.1 million people at airports across the country on Sunday, the most since March 7, 2020.
The new pandemic record marks the fifth day this month that air travel figures have exceeded 2 million passengers, about 75% of a normal day for the airline industry pre-pandemic.
But carriers are struggling to keep up with the crush of passengers. Flight-tracking site FlightAware says American Airlines canceled 6% of all flights on Sunday.
The airline cites labor issues with both its own crews and contractors and says it is rebooking passengers on new flights in advance through mid-July.