Airlines are reserving more seats for passengers willing to pay extra to be near a window, aisle or the front of the plane. That's making it harder for many families to sit together without coughing up roughly $25 more per ticket, each way. Booking early helps, and there are other ways to find adjacent seats:

- Visit the airline's website five days before departure. That's when some "elite" frequent fliers are upgraded to first class, opening up their coach seats. Another wave of upgrades occurs every 24 to 48 hours.

- Use ExpertFlyer.com, which notifies travelers for free when a window or aisle seat opens up. For 99 cents, it also sends an email if two adjacent seats become available.

- Check in 24 hours in advance when airlines start releasing seats held for passengers with disabilities or children traveling alone. Airline gate agents can sometimes put families in the few remaining seats set aside.

- Consider airlines like Southwest, whose passengers pick seats at boarding.