Aviation analytics company Cirium has revealed its airline performance stats for May, and Delta Airlines tops the list of the most punctual airlines, with the highest percentage of on-time arrivals among all major U.S. carriers. This is good news for anyone flying Delta, but the numbers, unfortunately, represent a decrease in on-time arrivals overall.

　　Of 147,000 Delta flights tracked in May, 81.04 percent arrived on time. As defined by Cirium, on-time arrivals are those that arrive at the gate within 15 minutes of the scheduled time. Delta is known for its reliability, and an 81 percent on-time rate is commendable, but according to Cirium, there has been a 5 percent drop in on-time arrivals from the previous month.

　　After Delta, the airlines with the highest on-time arrival percentages in May were Alaska Airlines (79.04 percent), JetBlue (76.58 percent), United Airlines (75.95 percent), Spirit Airlines (73.52 percent), American Airlines (69.64 percent) and Frontier Airlines (66.47 percent). The percentages for Alaska, JetBlue, and United all represent a decrease in on-time arrivals; however, this indicates potential issues as we head into peak summer travel season.

　　Another factor affecting travel plans is cancellation rates. Again, the news is not so great. Airlines and airports in North America experienced a 33 percent increase in flight cancellations compared to last month. Southwest Airlines and American Airlines experienced the highest number of cancellations in May.

　　TSA expects a very busy summer travel seasonand Memorial Day weekend proved to be a record-breaking oneso travelers should be prepared for delays and other hassles. Find Ciriums full report on airline performance in North America and around the world here.