New York (CNN Business) The excitement over Starbucks' holiday cups has reached 35,000 feet.

Alaska Airlines ALK is offering priority boarding to passengers who are holding Starbucks' holiday-themed coffee cups, who will be able to stand in an "espresso" lane. The promotion between the two popular Seattle-based companies begins Thursday and ends Sunday.

The promotion doesn't stop at the gate: Alaska said some passengers will find Starbucks treats on their seats. But it does come with some caveats.

Alaska Airlines will offer passengers holding Starbucks holiday cups board early.

Starbucks SBUX Although anyone holding thecup can board early, they won't be the first in line. That is still reserved for first-class passengers and elite members of its frequent-flyer program sitting in either cabin. Cup holders will board in the fifth boarding group, right before passengers sitting in the back of the airplane.

Passengers who board early and are holding a holiday cup don't get any additional perks.

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