Originally Posted by BenA

The service standard for "Delta One" flights is a predeparture beverage of orange juice, water, or champagne. Sometimes, Heineken is also offered, and you can usually request a mimosa. This was designed this way for international liquor reasons - they can provision just sparkling wine in the cart that has to be opened on the ground to save on taxes, and then once up in the air they unleash the full selection of the liquor cart. It also makes it easier for flight attendants to serve a larger cabin efficiently. (Unfortunately, Delta also puts super cheap sparkling wine in this cart: even if the up-in-the-air champagne is a nice $35 bottle, they pour $6 cava at the gate. Drinker beware.)

Domestic first class has smaller cabins and no tax considerations, so the full menu of predeparture beverages is available. First class service to Canada/Mexico/Caribbean/Central America also offers full PDB options, and I assume Delta just sucks up the tax implications on those flights.

It gets quirky with domestic Delta One, because the service standard is still the one designed for international flights - so if you're flying SFO-JFK, you'll get the champagne/orange juice/water package, which is intended to make you feel like you're flying an international flight. That's where it can get a little confusing.

While I don't always love the limited selection for Delta One PDBs, this definitely isn't new - it's been like this for as long as I've been flying Delta. Occasionally, an F/A will be able to hunt down an alternate PDB on request, but in general, Delta One flights are limited to what's available in the cart for on-the-ground use.