Airlines in the U.S. carried 58.4 million passengers in September, or around 80% of 2019 levels, continuing a strong recovery from earlier in 2021 but down considerably from levels seen in July.

The total in September was little changed from August on a year-over-year basis but marked a considerable drop from July when traffic recovered to 85% of 2019 levels, according to data provided by the Bureau of Transportation Statistics. Aside from the usual post-Labor Day decline in travel numbers, the drop can be largely explained by the emergence of the delta coronavirus variant of COVID-19, which peaked in August and September.

Travel numbers appear to be picking up moderately ahead of Thanksgiving. Passenger counts screened by the U.S. Transportation Security Administration reached an average of around 1.83 million in the seven days ending Nov. 16, compared to 2.15 million average in the same week in 2019, marking a decline of roughly 15%.

But with staffing levels greatly reduced from two years ago, it is likely that airlines will continue to be plagued by the kinds of operational meltdowns that caused cascading delays and cancellations at American Airlines, Southwest and Spirit Airlines in recent months, analysts say. 

“I do think you’ll see [staffing issues] interrupting holiday travel, and you’ll see that interrupting travel into 2022,” Bloomberg Intelligence analyst George Ferguson told Aviation Daily. “Industries that need a lot of labor are all competing for employees and the airline industry went through a really rough period during the pandemic. Some of these people—gate agents and ground crew and such—might decide that they don’t want to go back to aviation.”

As a result of rising labor costs, airlines are expecting to see unit costs surge in the fourth quarter from a year ago. All major airlines besides Alaska Airlines and Delta Air Lines are expecting double-digit CASM-ex increases in the fourth quarter, with the largest unit cost increases expected by JetBlue Airways (14-16%) and United Airlines (12-14%).

“The primary driver of that double digit inflation in CASM-ex is labor,” Ferguson said. “The airlines have said they’re going to over-hire, because I think they’re worried about losing people and they’re worried about attrition.”

Deutsche Bank analyst Mike Linenberg agreed with that sentiment, writing in a research note that staffing shortages and inflation may keep a lid on the amount of capacity airlines can deploy in 2022.

“The bottom-line is that the industry may find it far more challenging to bring on supply in 2022 given labor constraints and material cost considerations,” Linenberg wrote.