And sometimes goes to three.
Denver is definitely locked into an air travel game this year, as Air Force won't be in the field and no other Division I lacrosse program is close enough to Denver for a bus travel game. But other schools are at risk for involvement in an air travel game as well:
Jacksonville: If they make the tourney, they will have to play in an air travel game, as no other team in the field will be within 400 miles of Jacksonville. Could be sent to Denver if they qualify for that reason.
Duke: Figures to be a seeded team, and among programs close enough to Duke for a bus travel game, Maryland, Hopkins and Loyola all figure to be seeded teams as well. Virginia figures to qualify as an unseeded team, but I think the ACC would complain mightily if Duke-Virginia was a first round matchup. Towson and Richmond are the only remaining programs close enough to Duke for a bus travel game with a chance to qualify as an unseeded team. If both win, I think one will face Duke in the first round. Possibility that if one wins, that would be Duke's first round opponent as well.
Notre Dame: Both Detroit and Robert Morris can qualify for the tournament, but I don't think either one would face ND in the first round. Both, but especially the former, are strong candidates for the play-in game. If Ohio State makes the field (possibility, but not a lock by any stretch of the imagination), I believe they will be ND's first round opponent. Otherwise, ND likely gets an air travel game.
Yale/Maryland: I think these are likely the top two seeds in the field, and the 1 seed, who will get the play-in winner, is at significant risk for an air travel game. If Detroit wins the MAAC, they will likely be put in the play-in game and would be an air travel matchup for either team. If Canisius wins, they could travel by bus to Maryland, but not to Yale. So I think there is a decent risk for the #1 seed to be involved in an air travel game, although there are plenty of options to keep the #2 seed out of an air travel game.