Trade group Airlines for America expects the upcoming Labor Day holiday period to be the busiest on record.
A4A is forecasting 17.5 million passengers will fly on US carriers between August 28 and September 3.
That would represent a 4% increase on last year.
The most crowded day at airports will likely be Friday, August 30 when nearly three million travelers will head home or go on vacation.
The plane themselves will be more crowded than ever as dozens of Boeing Max jets remain grounded.
If it continues much longer airlines may have to consider buying or leasing more aircraft, A4A says.
"There is a lot of confidence that with all the attention and scrutiny given to this airplane that it will be in flight before they have to consider such extreme measures," said A4A economist, John Heimlich.
Despite the Max grounding the trade group says passenger traffic was up 4.4% in the first half of 2019, with an increase in revenue per mile of nearly 1%.
