"Because we aren't Santa Claus...THAT's why."
Travel in winter is fun. Invariably, when you plan a trip, Mother Nature throws some weather into the equation, and when it comes to flying, that understandably triggers apprehension in many people. (Hey, I live in Phoenix! Anything below 65 degrees triggers apprehension in me! "Honey! Where's my COAT!!!")
Flying in winter weather is far safer than driving on crusty frozen roads. In the air, you don't have to worry about another plane skidding on a turn and running into you. Planes in flight don't have to slow down in cold weather. Jet engines are easier to start than car motors in freezing weather. Even snow doesn't really affect airliners, until it's time to land. The best way to get traction when braking on snowy surfaces is to be really heavy. There aren't many heavier vehicles on rubber tires than an airliner. Plus, unlike cars, planes have reverse thrust. With reverse, on longer runways, I have landed just fine on icy runways, covered in snow. The hardest part was taxiing to the gate but, at three mph, even that wasn't too hard.
Snow is a hassle because it creates barriers to planes just as it does to automobiles. Drifts of snow build up and often times, airports run out of room to pile it up after plowing it out of the way in the vicinity of terminals. Or, it falls faster than the snow removal teams can remove it from the airport surfaces. Taxiways and runways have nifty blue edge lights. But, it sure is nice to see the other lights embedded in the center of the taxiway or runway. However, seeing those is not essential, even at night. That is why we Pilots slow down to a fraction of our normal taxi speed: We want to make sure where we are going and that we can stop when we get there.
A plane buried in snow overnight can be easily "de-iced" with hot snow/ice removal fluid and go on its way just fine, assuming the snow is not falling too heavily. Snow melting in the de-ice fluid dilutes this fluid, and eventually, it will freeze as if it is water. We call the time between de-ice and contamination, the "holdover time." Get airborne before the conservative holdover time expires and you are on your way. "Bust" that time and you are heading back to get de-iced again. The Pilots will confirm the plane is clean and safe for departure. If need be, you will see one of them in the cabin looking at the wings up close if there is any question whatsoever.
The only thing that really throws a "monkey wrench" into travel plans is freezing rain like that which recently hit Oklahoma. Freezing rain is caused when warmer air sits above colder air on the ground. Rain falls through the colder air and freezes on everything it contacts. Trying to de-ice a plane in these conditions is purely futile because there is no way to know how heavy the rainfall is. Unlike snowfall that accumulates much slower and is easy to measure by its affect of visibility, rainfall is hard to measure accurately. It doesn't take much freezing rain to shut down flying operations. Once the freezing precipitation stops falling, the planes can be hosed down with hot de-ice fluid and sent on their way.
So, when you look at The Weather Channel before your airline trip, don't be upset to see winter weather in your path or at your destination. Airports and airlines are experienced in dealing with messy weather. If they can safely get you on your way, they will. If they decide to err on the side of caution, it is because the airlines have learned how to safely operate in harsh winter environments. They will not cut corners just to get the plane airborne on time. And with operations slowing down as weather worsens, expect some delays in your travel schedule. To paraphrase a saying from my old days in the Air Force's Strategic Air Command, "Rigid Flexibility: The Key To Successful Air Travel!"
That said, unless you are heading into a blizzard or ice storm, expect operations to be pretty much normal. Expect a few delays and most likely, you will be pleasantly surprised to find your flight departing and arriving pretty much on time.
A very Merry Christmas and Happy Holidays From all the Crews and staff here at Southwest Airlines! I look forward to seeing you onboard one of my flights in the New Year!