Have you ever sat at the gate watching a long upgrade list dwindle to just a few names? While your fellow Delta Air Lines passengers are getting upgraded, you're wistfully crumpling up your boarding pass, indicating a middle seat in the back of the plane.

If you're sick of being on the outside looking in, here's how to get on a Delta upgrade list.

1. Reach Medallion status

If you're a Delta Medallion member, you're eligible for unlimited complimentary upgrades to Delta Comfort Plus and first class on all routes. In addition, day-of-departure upgrades to Delta One business class are available at no cost on flights within the United States.

Travelers flying internationally, however, aren't eligible for complimentary Medallion upgrades to either Delta Premium Select or Delta One.

When it comes to upgrade clearance timing — meaning when your new seat is confirmed — your elite status tier matters. The higher your elite level, the better your chance for an upgrade because top-tier members get priority.

For Medallion members, Delta Comfort Plus upgrades clear in the following order (based on availability).

And here's when Medallion members can expect a complimentary upgrade to clear for first-class seats (if a seat is available).

Holding either the Delta SkyMiles® Reserve American Express Card or the Delta SkyMiles® Reserve Business American Express Card moves you up on the upgrade list over other Medallion members at the same tier. Terms apply.

Note that basic economy fares aren't eligible for complimentary Delta upgrades. So if your budget is tight, be aware that you'll forfeit a potential upgrade by purchasing a basic economy ticket.

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2. Hold the right credit card

If you hold the Delta SkyMiles® Reserve American Express Card or the Delta SkyMiles® Reserve Business American Express Card, you qualify for complimentary upgrades to Comfort Plus or first class on domestic flights within the U.S. even without elite status. Terms apply.

Keep in mind that if you hold the card but don't have elite status, you'll be below all the Medallion members on the upgrade list, which may lower your chance of receiving an upgrade.

3. Use an upgrade certificate

Upgrade certificates are available only to Platinum Medallion and Diamond Medallion members as part of an annual Choice Benefits selection. They can be applied to Delta flights or flights operated by select partners.

Types of upgrade certificates

Delta offers two different upgrade certificates.

Regional upgrade certificates can upgrade you to first class or Delta One on flights within the U.S., Canada, Mexico, the Caribbean, Bermuda, Central America and Northern South America.

Global upgrade certificates are only available for Diamond Medallion members and can be applied to flights to all regions, including South America, Europe, Asia and Oceania.

Availability of upgrade certificates

The type of certificates available to you will depend on your Medallion status.

Platinum Medallion members who choose to receive upgrade certificates will receive four regional upgrades — global upgrade certificates are not available at this level.

Diamond Medallion members may receive a choice of one of the following:

Four global upgrades.

Eight regional upgrades.

Two global and four regional upgrades.

How upgrade certificates work

To apply an upgrade certificate to a booked ticket, call the Delta reservations line at 800-323-2323.

While using a certificate prioritizes your request over a complimentary Medallion upgrade, it doesn't guarantee you'll receive an upgrade. And depending on the classes of service available on your flight, you might end up on a waiting list.

For example, if you fly on an aircraft with a main cabin, Delta Comfort Plus, Delta Premium Select and Delta One, you can't jump straight from the main cabin to Delta One. Instead, you'll likely score a Delta Premium Select seat (as long as the upgrade clears) and then be added to a waiting list for a Delta One seat.

However, if the aircraft you're flying isn't configured with a Premium Select cabin, you can be upgraded directly to Delta One, as long as a seat is available.

The good news is you don't lose the upgrade certificate if there's no availability and you cannot use it. It simply goes back to your SkyMiles account until the next time.

It's worth noting that regional and global upgrade certificates expire at the end of your Medallion year. However, you can use them to upgrade other passengers traveling with you to avoid losing them.

Another option: Upgrade your Delta ticket using SkyMiles or cash

If you're not a Delta Medallion member, you have another option to upgrade your ticket — you can do it with the help of either miles or cash. Either method can upgrade a new ticket at booking or an existing reservation through "My Trips" in your SkyMiles account.

Typically, your SkyMiles are worth one cent each when upgrading this way. NerdWallet values Delta SkyMiles at 1.2 cents each, so we don’t recommend redeeming miles this way. However, if you've got the miles to burn, why not fly in a more comfortable seat?

If you want to receive a free upgrade on your next Delta flight ...

It's much easier to get upgraded for free if you have elite status with Delta, but you still have to compete for space with other status holders. Having the right Delta credit card helps those without status, but you must contend with elite flyers seeking an upgrade to those premium seats.

Upgrade certificates will place you higher on the upgrade list, and cash or a SkyMiles upcharge will put you there even faster.

However, if you want to secure a specific seat right away, the only way to guarantee it is by purchasing the class you wish to outright. Whether with cash or miles, paying for a ticket in a premium cabin is the sure way to get you the upgrade you want.