Discount carrier Southwest Airlines on Wednesday said increased security at airports after British police uncovered a suspected plot to blow up transatlantic flights hurt revenue in August.

But the airline said it flew fuller planes during the month compared with last year and that it was too early to know if effects of increased security measures would linger into the seasonally weaker winter months.

"We were impacted in the month by the security event," Southwest spokeswoman Beth Harbin said. "We are hoping it is a short-term blip... but we don't know that yet."

The US Transportation Security Administration banned liquids and gels, including toothpaste and shampoo, on carry-on bags on August 10, after British authorities said they foiled a plot to blow up planes using liquid explosives.

The restrictions forced more travelers to check luggage and increased the hassle associated with flying, hurting demand for air travel.

Continental Airlines on Friday said that elevated security concerns impacted its August passenger revenue growth, depressing it by about 1.5 points.

But airlines still benefited from what has been a strong summer and posted year-over-year gains in revenue and demand during August.

Continental managed to increase passenger revenue per available seat mile, or unit revenue, 6.5 percent to 7.5 percent, according to its own estimates.

Southwest said its load factor for the month rose to its best-ever level of 77.1 percent, up from 76.1 percent last year.