Yesterday I booked flights to Cusco, Peru on LA, but booked as DL codeshares with DL flight numbers. I called in to DL reservations because I specifically wanted to confirm the terms and make sure that if I needed to cancel/change my flights I would get a DL e-credit and not something usable only on LA.

The agent gave me a fare, for Latam flights in Light class but booked as DL flight numbers, and said the flights were changeable for a DL credit and miles-eligible. She then booked the flights but immediately said, "oh wait - those flights booked into DL E class and are actually basic," meaning they're non-changeable. So then she cancelled those flights and rebooked me into Main at a somewhat higher price, and now I'm in T/X fares. She claimed this was a "glitch" in the system, where flights show up as not basic until they're booked, and this is a known problem. That sounded odd, but who knows how the different airline systems work together.

Today, though, I went to Expedia to price out flights to Santiago, Chile, and there I see Latam flights in Light economy (booked as LA, not DL codeshares), and those flights are in N fare class. According to the DL website, N fares are not basic economy, and they earn DL miles.

So it seems that some Latam Light fares do book as basic economy for DL purposes, but others don't. Making things more confusing, Latam also does have a "Basic" fare class, which is cheaper and more restrictive than Light.

Does anyone know how this works? Are Light fares different depending on the country, or based on whether the ticket is issued as an LA or DL flight number? Thanks for any insight.