I spent five years traveling as a vegan. I also had better luck with Asian Vegetarian (AVML) than I did with non-dairy vegetarian (VGML). And, make sure you call the airline a couple of days before your flight, and give them the code you want (don't rely on them to look it up).

In terms of vegan meals, the asian airlines are the best (Singapore Air and Malaysian Airlines, in particular). I've found NW and UA to/from Asia to be pretty good, as well. Lots of grilled veggies, quite delightful fruit salads, and some strange varieties of pasta/noodles/rice dishes. I love the curries, particularly with chickpeas (NW, QF, and Air India!).

But, be prepared to get biscuits with lard, cheese, ranch dressing, milk chocolate, etc. No biggie, just ask FA for something extra.

And, beer, wine, and spirits are all vegan, right?