CHICAGO (AP) – Dense fog has caused flight delays and some cancellations at Chicago’s O’Hare and Midway international airports early on Christmas Eve during one of the busiest travel days of the holiday season. The Federal Aviation Administration briefly grounded flights at both airports until about 8 a.m. Tuesday and eased those restrictions as the fog cleared. By midmorning, nearly 50 flights had been canceled at O’Hare, and more than 70 flights canceled at Midway, split evenly between arrivals and departures.