Advance booking 

Charge 

At the airport 

Also of note:

AirTran 

The airline operates a first-come, first-served program; request when buying your ticket

 $20 each way (includes all legs of each journey)

Sure — if there’s anything left.

AirTran is notorious for its stingy seat pitch in its regular coach seats — as little as 30 inches on its Boeing 717s. $20 is a small price to keep the blood circulating down to your toes!

Alaska

Elite MileagePlan members, Full Flex fares and awards. Everyone else, nice try, but no.

No

Have a look when you check-in, either online 24 hours before departure or via kiosk. If there's anything left, it's all yours.

Want to feel like a second-class citizen? Fly Alaska without status. (Hope you enjoy the middle seat, all the way to Anchorage!)

American

AAirpass members, AAadvantage Platinum and Gold members, British Airways Premier, Gold and Silver members, those traveling on certain unrestricted fares

None

First come, first served — passengers may assign themselves exit row seats using the self check-in kiosks as well as by request in person from an agent.

Before you congratulate American on not charging for seats at the airport, consider why – they don't want them being bought out from under their prized elite AAdvantage members. (Without these guys, they're nobody.)

Continental

By next year, they'll be part of the same program as United, but for now, OnePass Elite members get in for free, while others can upgrade to an exit row after purchasing their ticket as part of the "Extra Legroom" program.   

Varies – $59 per flight is a typical average additional fee. (It's not cheap.)

No more freebies at the airport – they'll sell you one if any are available on the day of travel.

As on Alaska, it's often difficult to squeeze your way into the exit row at any price, thanks to the demand created by elite mileage program members.

Delta

Used to be a free-for-all, now only SkyMiles Medallion members and those traveling on unrestricted fares get to choose seats right away.

None

First come, first-served – get there early and look at the seat map at the check-in kiosk; if no dice, ask an agent and cross your fingers.

Become a SkyMiles member, even if you never intend to fly Delta ever again – you may get lucky and find some open seats before they are available to the  general public.

Frontier

EarlyReturns Summit members can reserve free at time of purchase, Ascent members can request for free at check in if pre-assignment not available.

These seats now fall under the "Stretch Seating" designation; from $15 on up each segment for economy fares, from $5 for "Classic" or free for "Classic Plus", each way depending on length of flight.

At time of purchase or at airport if any seats left.

Like any other airline that follows this policy, the early bird gets the worm on the day of departure.

JetBlue

Seats are sold as part of the airline's "Even More Legroom" priority seating program; there are no freebies.

The cost is steadily rising -- $30 for shorter flights, $65 or more for transcontinental

Can be purchased at time of booking, or on day of travel or at online check-in if any seats remain.

Passengers buying these seats have priority boarding privileges – essentially, this is JetBlue's version of First Class plus fast track TSA lines at some airports. (And we've seen attendants boot freeloaders with no apologies.)

Southwest

No

N/A

First boarded, first served

Southwest doesn't assign seats, but if you buy a higher-priced "Business Select" fare you get to board the plane in the first portion of the 'A' boarding group, so your chances of grabbing an exit row are greatly enhanced. You also get a free cocktail and other perks.

Spirit

Available for purchase any time.

$20

First come, first served

For $5 more, stretch out (well, all things being relative – this is Spirit we're talking about) in the comfort of their $25 Big Front Seats.

United

 Elite Mileage Plus members (Premier, Premier Executive, and 1K) get automatically upgraded to the Economy Plus seating, which includes exit rows. Everyone else pays.    

No fee for elites, charged based on distance traveled, sometimes over $100 per leg.

Economy Plus is sold until it’s full — you may buy all the way up to the gate.

On many flights, even Premier MileagePlus members can't get near the exit rows or the Economy Plus seating, so don't feel bad if you strike out.

US Airways

Exclusively reserved for Dividend Miles Preferred members.

No charge

Any remaining seats are made available at the airport.

Sign up for Dividend Miles; non-Preferred members can access Preferred seats 24 hours before scheduled departures. You never know.  .

Virgin America

Exit rows are part of the "Main Cabin Select" section; fares are significantly higher than economy. 

On a recent flight from LAX-SFO, economy was $89, Main Cabin Select was $190.

Can purchase at airport based on availability.

Not worth the extra money, unless you need lots of leg room on a transcontinental run. JetBlue's a much better bargain, though. VA throws in more bells and whistles, but the fact is you're overpaying for an economy seat. No amount of free movies can take the sting away.