He says the big problem is crews and equipment aren't in their usual locations. Pilots and flight attendants are out of their rotations. The airlines usually need 36 hours to get back up-to-speed - meaning midday Friday.
What should people do who have tickets for Thursday flights? Ask your airline to change your itinerary. Most are doing it for free -- not refunds -- but most will let you rebook on another flight and date without penalty.
Trouble is, if you had reservations for Wednesday or have them for Thursday, your odds of getting rebooked on a flight Friday, the beginning of Presidents Day weekend, not to mention Valentine's Day, are slim and none. Those flights are already booked solid. In many cases, passengers are being told they'll be held up until Sunday. And Monday, being a holiday, is a tough day as well.
If you must travel today, Greenberg suggests seeing if your carrier will rebook you from an alternate nearby airport - for instance, Islip International, on Long Island, instead of the three major New York area airports, or Milawukee instead of Chicago, or Providence, R.I., instead of Boston.