How do you keep O'Hare open in a blizzard?
Removing snow from runways and taxiways marks only the first step that city aviation officials must take to safely prepare Chicago's airports for the severely limited number of flights expected to resume on Wednesday, following curtailed operations on Tuesday.
It will be a time-consuming process to plow and brush snow off miles of pavement. Several runways at O'Hare International Airport are more than 2 miles long and 150 to 200 feet wide, and O'Hare has dozens of additional miles of taxiways.
Salt and chemical de-icers that are customarily used on roads cannot be applied to airfield pavement because the corrosive materials would damage the metal-skinned aircraft.
Once the airfields at both airports are cleared off and pass an initial inspection, Chicago Department of Aviation vehicles will test for slippery spots by conducting braking tests. The information will be passed along to pilots and air traffic controllers.
When flight operations resume, the pilots of the first planes to land will radio their more accurate stopping-distance readings to O'Hare tower, which will pass along the data to pilots on a final landing approach.
But before any of that occurs, city aviation crews will scour the runways for possible debris that, if left on the airfield, could be sucked into jet engines or penetrate the thin skin covering the fuselage and wings.
Runways at Midway Airport are shorter than those at O'Hare, a factor that limits airplane size to no larger than a Boeing 757. Southwest Airlines, the dominant carrier at Midway, operates Boeing 737 aircraft.
Midway remained officially open on Tuesday, but by midday airlines completed their downsized flight schedule for the day.
Airlines were expecting to restart operations Wednesday afternoon at Midway. The Southwest Side airport's relatively short runways -- the longest runway at Midway is only 6,521 feet long -- will require airfield crews to keep the pavement especially pristine after the snowstorm.
The Federal Aviation Administration several years ago revised the minimum stopping distances that pilots are required to calculate before attempting to land. The change was made in the wake of a December 2005 accident in which a Southwest jetliner skidded off the end of a ice-contaminated runway and crashed through airport fences. A 6-year-old boy riding with his family in a car was killed when the plane struck their vehicle in the intersection of 55th Street and Central Avenue.
The results of all the preparations to restore O'Hare and Midway to normal operations will depend on whether the Chicago gets socked with more snow.
An equally important factor will be the whereabouts of planes, pilots and flight attendants across the vast airline system. The airlines for years have proactively canceled flights on the eve of severe weather, after learning the hard way when they implemented no major changes and it took days to reposition aircraft and crews.
The massive cancellations before Tuesday's blizzard were intended to minimize the inconvenience to passengers, but also to route planes to cities that are the least impacted by foul weather. Such a strategy increases the chances that planes will be able to operate the next day, and it shrinks the recovery time frame, officials said.