I get why this is a tough call. $1500 isn’t pocket change, but for Lufthansa First it’s also not some insane upgrade price. Especially if you’re not paying for the business ticket yourself, it feels like a rare chance.
That said, you’re missing a big part of the magic by not flying out of FRA. No First Class Terminal, no full ground experience. In MUC, First is nicer than business, but it’s not life changing. Onboard will obviously be better, but LH business on the A350 is already solid.
Mileage and status wise, this won’t really move the needle. You’ll almost certainly still earn based on the original business fare, not First, and one First flight won’t suddenly unlock anything meaningful in Miles and More.
If you’re doing it purely for the experience and won’t miss the $1500, sure, it’s a cool story. If you’re hoping it’s some once in a lifetime transformation or status shortcut, probably not worth it.
0