Recently, industry trade group Airlines for America said they expect a record 234.1 million passengers to travel worldwide on U.S. airlines this season, a reflection of vacation-hungry families, low oil prices and overall strong demand for air travel.

That's good news for airlines, yet full planes — and the extra fees many airlines charge for preselecting a seat – means families may have trouble getting seated together on airplanes, making it likely adult travelers may find themselves planted next to cranky children.