We've done it a few times. From the US and from Europe. I am going to give you a trade secret. It is cheaper than upgrading but makes your flight first class, well, almost first class. We check which plane we will be flying on. From there, you can find out how many crew members will be on your flight. We buy some small mesh bags and fill them with chocolates, thank-you notes, a small trinket or toy, and the equivalent of 1 Euro in whatever currency you have locally. This is the van tip. The attendants all have a van that takes them to their lodgings, and they tip the van driver. I have had champagne brought to me, extra pillows, cheese plates, wine, and tons of attention. Once we were given merch from the first class. In all, it cost me about 30 Euros. The gratitude alone was worth it. Those attendants have a pretty crappy job.
