Yet another complaint to add to the countless grievances air travelers have about America’s airlines: Their on-time performance is among the worst in 20 years.

In the six months to June, US airlines left late nearly 21.94% of the time, the lousiest on-time departure rate of the last two decades. That’s according to the US Department of Transportation’s monthly Air Travel Consumer Report and data crunched by the Bureau of Labor Statistics. Flights arrived on time only 74.17% of the time, and the average flight cancellation rate was 3.3%, worse than all but three of the last 20 years.

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In June, the worst-performing airlines for timeliness were commuter carriers: Envoy (formerly American Airlines subsidiary American Eagle) and ExpressJet (which operates for Delta, United, and American). In the six months to June, flights dubbed by the DOT as ”chronically delayed” were dominated by Envoy, ExpressJet and SkyWest, which flies for US Airways, Alaska Airlines, United, American, and Delta.

The worst-performing airport was Chicago’s O’Hare, the only airport in the country boasting two big domestic airline hubs (United and American). The airport’s on-time rating in June was 59.61%; in the six months to June, more than a third of all O’Hare flights ran late.

The delays may only get worse. United and American, which rank worst among major legacy carriers for on-time performance, are reorganizing their flight schedules to boost profits. The tactic involves cramming arrivals and departures into shorter time frames. American has said this allows for quicker connections, but it also clogs gates and runways when things don’t run smoothly—for instance, during bad weather.