It seems like a Blue Line detour is the least of the worries for travelers out of O'Hare. From January to May of this year, O'Hare reported the worst on-time record of major U.S. airports, falling from 64.4 percent last year to 63.2 percent this year. This in spite of the fact that the total number of flights was reduced by 4.6 percent, thanks in large part to major flight cutbacks from American and United.