It really depends on your flight. Last year, expecting massive crowds, showed up at Logan at 05.45 the Tuesday before Thanksgiving for a 7.25 flight to RSW. Not only was the queue only 10 min long, but there was no one in the terminal. The year before I flew to Minnesota, also the Tuesday before Thanksgiving. We did curbside check-in (something you should consider when travelling during busy seasons), and were checked-in in about 10 min. I do advocate being there early, but don't overdo it, especially if travelling with children, because things may go better than planned and you're stuck in an airport with 90 min to spare. But leave your options open. Consider alternatives like curbside check-in. Also, if getting close to departure time, contact an airline personnel, tell then your flight number, and they'll usually bump you to the front of the queue. Remember no airline wants people to miss their planes.
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