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Snow delays

By Lester Holt, NBC News anchor

Lots of holiday reunions and vacations are in flux tonight as the airlines deal with this massive snowstorm hitting the East Coast. Thousands of flights have been canceled, impacting travelers across the country. With the airlines already operating fewer flights than they used to, and passenger loads traditionally high this time of year, it could take days for some people to be re-accommodated on other flights.

I've covered aviation for many years, and I'm often asked why airlines cancel so many flights before the storm even arrives? Here are some of the reasons: Airlines have to consider not only where their airplanes are, but where their pilots and flight attendants are too, and where they may potentially become stranded.

Once weather delays start in a particular region of the country, flights destined for those places end up stuck at their departure gates, blocking incoming airplanes from parking and disembarking their passengers. Taxiways quickly become crowded, and every minute a plane waits on the ground with passengers, the clock is ticking against the maximum number of hours flight crews can legally work.

So, when big storms approach, airline staffers inside high-tech operations centers -- usually working with their own meteorologists -- begin to execute a plan designed to make sure they have their airplanes and crew members available in the optimum places to get things back up to speed as soon as possible after the weather passes. Yes, modern jetliners can land in almost zero visibility. However, the runways and taxiways have to be reasonably clear of snow, requiring airports to suspend operations at some points to allow the plows to do their jobs.

Finally, another big source of delays in snowy weather is the need to de-ice airplanes before takeoff. This is a delay you should be happy about! Even a thin coating of ice on a wing can rob a plane of critical lift during takeoff and cause an accident. Planes must be sprayed with special de-icing fluid before takeoff, and if they are not airborne within a specific amount of time, the process has to be repeated. Again, don't grumble over this one. Taken together, these factors -- and many others -- if not managed properly, can be a recipe for airport grid lock. The philosophy of airlines is that it is far better to begin strategically canceling flights in the face of approaching storms rather than risk a massive meltdown, and a longer post-storm recovery.

I hope all of you safely make it to your holiday destinations. We'll have a lot of today's massive storm on tonight's NBC Nightly News.