Delta Air Lines led in the August rankings for on-time performance (OTP) by a North American carrier, according to the latest report from Cirium, an aviation analytics provider. The carrier’s OTP was 83.9%, up almost seven percentage points over July. Spirit Airlines remained in second place at 78.5%, up nearly 2 percentage points. Alaska Airlines ranked third at 77.4%, an increase of 2.2 percentage points over July.

North American on-time performance overall rose 4 percentage points to 75.8% for the month. Southwest rose to fifth place from seventh on a 6.8 percentage point jump in OTP for August. WestJet was the only airline with declining performance (down 1.5 percentage points) and falling to last place in the Top 10. Frontier rose 5.9 percentage points to 70.8% to take ninth place for August.

Delta was the only North American carrier on Cirium’s global list of top on-time carriers, which in August was led by Azul at 92.2%.

Southwest had the highest completion rate among North American carriers at 99.7%. The top three carriers for on-time performance in August all had completion factors above 99% —Spirit at 99.8%, Delta at 99.3% and Alaska at 99.2%.