Flying with kids or in a large group can be tough, which is why it’d be ideal for families to be able to sit together. But now that some airlines are reserving window and aisle seats for customers willing to pay extra for them, or frequent fliers, it could mean some families having to split up on the plane.

Airlines want the extra revenue for the window and aisle seats, at $25 or more each way, so some families looking to reserve seats online after they’ve booked a flight are frustrated when it appears only middle seats are available, notes the Associated Press.

Since last summer, American, Delta Air Lines, Frontier Airlines and United Airlines have increased the percentage of coach seats requiring an extra fee. Some – like those on Delta, JetBlue Airways and United – come with more legroom. Others, including those on American and US Airways, are just as cramped but are window and aisle seats near the front.

Allegiant Air and Spirit Airlines go one step further, charging extra for any advanced seat assignment. On Spirit, passengers who aren’t willing to pay the extra $5 to $15 per flight, are assigned a seat at check-in. The computer doesn’t make any effort to keep families together.

Some families balk at the idea of shelling out more money in fees when it’s already expensive enough to go on a family vacation with the price of airline tickets this summer expected to rise.

Buying tickets in advance can help, and even if you don’t, gate agents are often helpful at grouping families together when the time comes. And right before it’s time to fly, many airlines will release those seats they’ve held in reserve for their frequent fliers or fee-payers, at no extra charge.

Your best bet to sit together is to try for those advance seating assignments. If you’ve booked through Orbitz, Expedia or another travel site, make sure to confirm those seat selections with your airline.

Forced to fly solo, even on family vacations [Associated Press]

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.