Chicago’s two major airports had more departure delays in May than any other airports in the country. The U.S. Department of Transportation also reports O’ Hare is the world’s busiest airport for total number of flights.

Aaron Gellman, an expert on transportation for Northwestern University, says the increasing number of delays isn’t cause for concern.

“They’re both among the busiest airports in the country and therefore they are often quite congested and of course we’ve had some fairly difficult weather during that period and I wouldn’t draw any conclusions on one month’s data anyway,” he suggests.

Nonetheless, Gellman says the delays highlight the need for an expansion of O’ Hare.

The report also says Midway handled 3 percent more flights in the first six months of 2006 compared to the first half of 2005.