As the peak summer travel season recedes and ticket prices fall, the number of US airport security checks fell to the lowest level since May.

According to data from the US Transportation Security Administration (TSA), the number of passengers passing through security checks at US domestic airports on Tuesday was 1.35 million, the lowest level since May 11.

Travel demand usually falls in late summer as students return to school. Executives of airline companies such as Southwest Airlines and American Airlines warned last month that expected revenue or profits would fall short of expectations, and airline ticket reservations were weak due to the increase in COVID-19 delta variant cases.

Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention (CDC), recommended on Tuesday that people who have not been vaccinated against COVID-19 should not travel during the Labor Day holiday.

According to a report by Deutsche Bank, domestic ticket prices for most American airline companies were lower for the week ending August 27 compared to the previous week.

For tickets purchased 21 days in advance, the average one-way domestic fares of Spirit Airlines and JetBlue declined by 30.6% within a week to 51 US dollars and 183 US dollars, respectively. The average domestic one-way fare for American Airlines dropped nearly 23% to $158, Delta dropped more than 20% to $150, and United Airlines dropped more than 25% to $199.

United Airlines said on Wednesday that it expects to carry 2 million passengers between September 2 and September 7 (including Labor Day weekend), about three times that of last year, but still lower than 2.6 million in the same period in 2019.