That's not really a fair analogy. It's difficult (or impossible) to predict major events like terrorist attacks or weather phenomena that cause phone circuits to overload. And when these events occur, telecom companies lose money.

But flights fill up every day. When they do, airlines maximize profit.

Agreed, major phenomena are exceptions to the norm, did not intend to convey any judgement on the practice. Those same phenomena affect airlines too. In fact, weather delays had hampered United's ops leading up to the ejection event in the news. My point was airlines are not the only ones who sell > capacity.