Back in 2011, CrankyFlier published a great article on why codeshares are awful and how they provide no benefit to the traveling public.
Unfortunately nothing has changed here, and codeshares continue to provide nothing but confusion. Passengers flying wholly domestic US routes still see codeshare flight numbers from all manner of international airlines like KLM, Singapore Airlines, and Qatar Airways displayed at gates and on departure boards. It’s an absolute mess, and as more airlines ink codeshare agreements, it’s only getting worse.
There are only a handful of ways savvy travelers can use codeshares to their advantage. As mentioned in the article, employees on government-funded trips (bounded by the Fly America Act) can utilize codeshare flights to fly “American” carriers while actually traveling on a foreign partner airline. There are also a couple fun tricks regular folks can use to get lower fares or optimize FFP earnings.
Frequent travelers will find that it’s usually best to book directly with the operating airline, using its own flight number (the “prime” flight number). You’ll enjoy a more seamless experience that airlines have most thoroughly tested. Booking codeshare flights (for example, Alaska flights with AA codes, or vice versa) will only cause headaches when it comes to making changes or enjoying reciprocal elite benefits like preferred seats and upgrades.
But sometimes, codeshares can offer different inventory on the same flights, and they can also earn vastly different amounts of miles or qualifying dollars towards frequent flyer status. For example, you may find completely different inventory on Oneworld carriers such as American, British Airways, Iberia, and Finnair. It’s possible that an AA flight under an AA code will only have mid or high level booking classes available, while the lowest O or Q booking classes might be available on the same AA flight using a BA code… which might only be bookable using an ITA Powertools deeplink for AA.com1. You may even find different fuel surcharges depending on the codeshares used. This can cause huge variation in the final ticket price, and is often worth playing around with.
And then there’s frequent flyer program earnings to consider. With American and Delta at least2, you’re rewarded based on ticket price for flights sold with their own codes, but for codeshare flights, you’re given miles and status based on the distance traveled. In this way, codeshares allow you to choose how you want to earn; naturally, it’s to your advantage to book Delta flights with DL codes on expensive and/or shorter trips so you can enjoy greater rewards for the high spend, but KL, AF, or VS codeshares would enable you earn based on distance when you find a great deal on a long haul trips.
In an ideal world, airlines would do away with codeshares, and flights would simply always be marketed by the operating carrier. This way there’s no confusion about who is taking you from A to B. There’s no need for an airline to place its code on other airlines’ flights, as interline agreements already permit combining flights on multiple airlines with a single ticket. Pricing and inventory could be harmonized, so there wouldn’t be arbitrage opportunities by finding the optimal combination of operating, marketing, and ticketing carriers. But until this changes, be on the lookout for price discrepancies you can take advantage of to beat airlines at their own game.
For international flights, the marketing carrier (the airline whose codes are used for the long-haul segments) is typically also the ticketing carrier. But with the help of Powertools deeplinks, you can make AA.com sell you e.g. BA-coded transatlantics (even for AA-operated flights!) that would never appear organically on AA.com, and which may offer lower fare buckets than their AA counterparts! ↩
United will give you miles based on spend if you book with them (016 ticket number), regardless of codeshares used. ↩