Wine country trips usually end with an awkward decision at the airport: pay overweight-style baggage fees for that case of Cabernet, ship it at eye-watering cost, or leave it behind. Delta has a new answer for California travellers. Its "SkyMiles Wine Takes Flight" programme lets eligible members check one case of wine at no baggage charge when departing five Golden State airports.

The airports in on the launch are Oakland, San Francisco, San Jose, Sacramento and Sonoma County - effectively the whole catchment for Napa, Sonoma and Livermore Valley tasting rooms. Delta says it plans to add more airports over time, so this may just be the first chapter.

Here's what counts as a free case: a single box or wine travel container holding up to twelve standard 750ml bottles, weighing no more than 50 pounds and within the usual 62 linear inch checked bag limit. Bottles must be unopened with original labels, and packed in a sturdy, leak-resistant container with proper padding. You'll hand it over at the ticket counter, and if staff want to inspect it, the container can't be sealed beforehand. Delta reserves the right to refuse anything questionably packed.

The eligibility rules are refreshingly loose. Any active SkyMiles member aged 21 or over qualifies - no Medallion status needed, and both paid and award tickets work. Better still, if you do have status or a Delta co-branded credit card, the wine case doesn't even count against your free checked allowance. Note the fine print: the perk applies only on departure from a participating airport (flying a case into San Francisco gets you nothing), codeshares are excluded, and the wine travels at your own risk.

Why bother? A standard checked bag fee runs around $35-40 each way for many travellers, so this effectively wipes out the cost of bringing home a case. It's also one of the few genuinely useful things you can get from a free loyalty membership - sign up for SkyMiles on your phone in the tasting room queue and you're covered. The programme suits anyone doing a Napa or Sonoma long weekend who'd otherwise pay to check bottles or risk them in a cardboard box in the overhead bin.

One caveat from hard-won experience: saving the bag fee means little if all twelve bottles arrive as a sticky mess. Invest in a proper wine travel case with dividers and shock absorption, or use the shipping-quality packaging some wineries sell. And remember that only the first case is free - a second one, or anything overweight or oversized, gets charged as normal.