Darvocet and Darvon are classified as narcotic pain relievers. Its formula lists acetaminophen and Propoxyphene as its two major active ingredients. Darvocet contains a combination of propoxyphene and acetaminophen. Propoxyphene is in a group of drugs called narcotic pain relievers.
For general members, this is 24 hours in advance. The amount of   If a flight has seats available in First Class or Business Class, its less than 24 hours prior to the flight, and there is no one on the wait list, United may begin to sell upgrades at check in.
At the low end, United's Economy Plus upgrade offers pretty much only a bit more legroom, while Virgin America's Main Cabin Select offers larger seats, complimentary food and drink, priority check-in and security screening where available, priority boarding, and a free checked bag.