Quick Take: Book premium economy for the price of a coach seat on select widebody domestic routes

Although the “Big Three” US airlines operate single-aisle aircraft — such as the Airbus A320 and Boeing 737 — For most popular domestic routes, United Airlines, American Airlines and Delta Air Lines all operate twin-aisle jets.

Airlines often use wide-body aircraft on long-haul flights, so they often offer a better in-flight experience (with features like seatback TVs, power outlets, and larger overhead bins). But the best part of these wide-body aircraft is undoubtedly the ability to book top economy seat for the price of a seat with extra legroom.

Here’s what you need to know to get a “free” upgrade to premium economy on your next flight.

Related: The Complete Guide to Booking Premium Economy Class Tickets Using Points and Miles

How to find ‘free’ premium economy seats

Except for a few cases where airlines sell premium economy as a separate cabin (mostly long-haul flights to Hawaii and some transcontinental services operated by Delta), you can book premium economy on many domestic widebody flights as United Economy Plus, American Premium Economy Class or Delta+ Comfort.

That means you can use your free extra legroom seat—an elite perk—to book a premium economy seat. You can pay to choose these seats if you don’t have elite status. Expect the same perks and service as you would in an extra legroom seat, but of course, premium economy is better.

When booking a flight, check the type of aircraft operating the flight. Pull up the seat map if you see a wide-body aircraft like an Airbus A330 or A350, or a Boeing 767, 777 or 787.

If you know how to pay attention, you can tell if the seat is premium economy or not.

First, the seat configuration will be different from the rest of the economy cabin. On Boeing 777s, like the one above, the most common premium economy seat configuration is 2-4-2 instead of the standard economy seat of 3-4-3. This is because premium economy seats are wider.

Also, in case United Premium Plus ClassThe row numbers of the Premium Economy cabin (rows 20, 21, and 22) are significantly different from the rest of the Economy Plus cabin (rows 30 to 34, 40, and 41). All blue seats, including the Premium Economy seats, are available for booking as Economy Plus on this aircraft. This means that Premier Silver members are eligible to receive them for free at check-in. Premier Gold, Premier Platinum, Premier 1K, and Unified global service Members can select their seats when booking at no charge — and United’s generous Economy Plus rules still apply.

American makes it a little more complicated. You can’t tell from the row number that you’re in premium economy, so pay attention to the seat layout on the seat map. Premium economy is in a 2-3-2 configuration on this plane, as opposed to the standard 3-3-3 configuration on the rest of the plane.

All orange seats, including premium economy, can be booked as Main Cabin Extra seats (American’s extra legroom seats) on this flight.

Delta Air Lines, which tends to have larger premium economy cabins than United and American, designates some domestic premium economy seats as Comfort+. If you Medal status By allowing you to use Comfort+ for free, you can win one of these seats for free.

If you are not satisfied with the premium economy seats available when you book your flight or if all premium economy seats are taken, book Flyer Expert Seat reminders. (ExpertFlyer is owned by TPG’s parent company, Red Ventures.) You’ll get an email alert if a seat becomes available. ExpertFlyer has saved me from a middle premium economy seat several times.

Related: How to use ExpertFlyer alerts to get better seats

Premium economy class vs domestic first class

Now comes the fun part.

Premium economy seats are significantly better than standard extra legroom seats. Instead, they’re closer to what you’d get in domestic first class with an aisle seat.

Compare seat sizes using United’s fleet. These measurements come from United website.

As you can see, the width is not as spacious as the first class cabin on a Boeing 737; however, the pitch and recline are more spacious than the narrow-body first class cabin.

So, let’s go back to this example.

For $397, Premier Gold members and above can book a premium economy seat—the equivalent of a first-class seat that sells for more than $3,000. Of course, first-class seats come with a proper meal, extra checked baggage, Premier Access, and better service. But the two are about equal if you just look at the seats.

United may change the equipment, perhaps moving you to a standard Economy Plus seat, but in my experience that only happens occasionally.

Related: Why United’s Expanded Premium Plus Program Is More Than Just Good News

Domestic flights by wide-body aircraft

Here are some domestic flights that United, American, and Delta typically fly widebody on (at the time of writing). In our testing, you could book premium economy as an extra legroom seat on these routes. As you can see, these are high-traffic routes to, from, or between hubs. These routes are subject to change.

Unify

• San Francisco International Airport (SFO) to Washington, DC’s Dulles International Airport (IAD), Houston’s George Bush Intercontinental Airport (IAH), Chicago’s O’Hare International Airport (ORD), Honolulu’s Daniel K. Inouye International Airport (HNL), and Kahului Airport (OGG) on the island of Maui
• Los Angeles International Airport (LAX) to IAD, ORD, HNL and IAH
• Denver International Airport (DEN) to ORD and IAD
• Newark Liberty International Airport (EWR) to IAH

Please note that United also operates multiple daily premium economy services from SFO and LAX to EWR that are sold as separate cabins.

American

• Miami International Airport (MIA) to Dallas Fort Worth International Airport (DFW), Phoenix Sky Harbor International Airport (PHX), Charlotte Douglas International Airport (CLT), Tampa International Airport (TPA), LAX and ORD
• DFW to Orlando International Airport (MCO), Cancun International Airport (CUN) in Mexico, ORD and LAX
• Philadelphia International Airport (PHL) to CUN and PHX

Delta

• Hartsfield-Jackson Atlanta International Airport (ATL) to Boston Logan International Airport (BOS), Minneapolis-St. Paul International Airport (MSP), Seattle-Tacoma International Airport (SEA), Detroit Metropolitan Wayne County Airport (DTW), New York City’s John F. Kennedy International Airport (JFK) and LAX
• LAX to DTW

Related: Perfectly Fine, But Nothing More: American Airlines Premium Economy Class Over the Atlantic

Last line

In addition to a private cabin near the front of the plane, premium economy seats typically offer in-flight entertainment with remote control, more comfortable reclining seats, a small legroom, and (my favorite) a tray table in the armrest that’s wide enough to avoid elbow bumps with your seatmate.

While your airline can always change its aircraft type, booking premium economy for the price of a seat with extra legroom is one of the best domestic flying tips. The next time you see a widebody jet on a flight you’re considering booking, remember that some seats with extra legroom may be much better than others.