Every day around noon, a line of Tupperware containers forms near the kitchen microwave in our office.
More often than not, when one item is finished cooking the owners of the other containers are nowhere to be found. Is it inappropriate to "jump" the queue and microwave my own food, or should I wait for the others to show up and cook theirs first?
There’s an old saying that fits this situation perfectly: You snooze, you lose. If the machine is empty and people in front of you have left to do something else, they’ve forfeited their position in line. Maybe they answered a phone call and will be tied up for several minutes—the reason doesn’t really matter. So go ahead, put your item in the microwave, and wait there while it cooks. If the other person returns, smile and say politely, “I wasn’t sure how long you might be, so I went ahead and started mine, just to keep things moving. I’ll be done in just a minute.”
Source: Post, Peter. "Etiquette at Work." Boston Globe 1 Jan. 2006.