A band of storms caused thousands of cancellation and delays at the start of a long holiday weekend.
A day after airline executives met with US transportation officials on how to stem flight disruptions, more than 10,000 flights were late or scrubbed.
Pete Buttigieg went to New York after his flight was canceled.
"That is happening to a lot of people, and that is why we are paying close attention to what can be done and how to make sure that the airlines are delivering."
The system returned to normal on Saturday due to calm weather. The rest of the country was recording below average delays. Juneteenth is a public holiday on Monday, which is the start of a three day US weekend.
The airline chiefs were reminded by Buttigieg of the need to reduce impacts from delays. The department has the power to regulate consumer protections. Most of the delays are the result of weather.
There were delays at large airports in Atlanta, Charlotte, Washington, D.C. and New York due to the storms. It is more difficult to respond to bad weather because of the airline staffing problems and the rebound from the Covid-19 Pandemic.
The totals are about 12% below the year before.