Delta significantly improves Global Upgrade Certificates on partners

Each year, top-tier Diamond Medallions get a pick from an exclusive collection of Choice Benefits.

The options range from 25,000 bonus SkyMiles to a Sky Club membership to a $200 travel voucher and more. Here at TPG, one of our favorite Choice Benefits are Global Upgrade Certificates (GUCs). These upgrade vouchers are valid on Delta and select partner flights for a one-way bump into business class.

Well, Delta's Global Upgrade Certificates just got even more valuable.

Specifically, the Atlanta-based carrier has sweetened the deal for those looking to upgrade flights operated by Air France or KLM, as confirmed by a Delta spokesperson to TPG.

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Let's start with the best news — you can now use a Global Upgrade Certificate to upgrade from coach to business on Air France.

Previously, redeeming GUCs on Air France was one of the poorest redemption opportunities. That's because you could only confirm an upgrade from coach into premium economy or from premium economy to biz. But you could never bump two cabins (like you can on Delta-operated flights).

But that's not all.

Upgrades to Air France business class are now cleared into the "Z" class of service. (Previously, it was the "O" class of service.) This is also great news since the "Z" class of service is much more readily available than the "O" class. The former is used for discounted revenue business-class fares, while the latter is reserved for business-class award tickets.

And again, that's not all.

Delta is also expanding the eligible fare classes that qualify for a GUC. Previously, you needed to purchase a really expensive, flexible coach fare class (Y, B or M) to be eligible for a bump to Air France's premium economy.

Going forward, you can book discounted coach tickets and still qualify for an upgrade to business class. The exact eligible fare classes differ based on which carrier issued your ticket. For Air France-operated flights sold by Delta, the following coach fare classes are eligible for an upgrade to biz: Y, B, M, H, Q, K, L, U, T, X or V. Additionally, all Air France premium economy fares booked on either Air France or Delta can now be upgraded into business class with a GUC. For the exact fare classes eligible for an upgrade, check out Delta's site.

Related: Everything you need to know about airline fare classes

Finally, the carrier is also lifting the restrictions on which AF flights are eligible for a GUC.

Diamonds can now apply a GUC on any Air France long-haul route with a distance of at least 1,750 miles. That means that you can upgrade a one-way itinerary from New York to Istanbul via Paris using a single GUC.

Additionally, you can now upgrade tickets on Air France or KLM that were sold by Air France, Delta or KLM.

If a call center agent hasn't yet heard of these updates, refer them to Delta's Global Upgrade Certificate terms at the bottom of the Medallion Upgrade webpage.

While long-haul international travel is still largely off-limits, these improvements come at the perfect time for many newly minted Diamond Medallions. Through the end of October, Delta is offering a targeted status match challenge up to Diamond status. If you fly six qualifying round-trips or 12 one-ways during the promotional period, you'll receive Diamond status through Jan. 31, 2022 — and get a pick from the Choice Benefits.

Of the Big 3, Delta and United let top-tier elites use confirmed upgrade certificates on select partner flights. You can use United's PlusPoints to upgrade flights operated by ANA, COPA or Lufthansa. American Airlines, on the other hand, doesn't let Executive Platinum elites redeem systemwide upgrades for partner flights.

It's not only good news from Delta on Wednesday. The carrier recently increased the cost of many partner award tickets. Additionally, the carrier is now charging more miles for flights booked between 21 and 59 days before departure and even more miles for those booked within 21 days.