One more thing you can try to do is that if you have DL GM, try to status match to UA Gold, which gives you United Club to access for international trips. In addition, for ORD-VIE non-stops, you can actually access to ORD Polaris lounge now, which is the best lounge among US3 legacy airlines by a large margin. UA has improved quite a bit this year, and you wouldn't be disappointed.