By Lila Battis
January 07, 2016
Delta Airlines

Last year was a banner one for airlines: Thanks to increased fee revenue and a 40 percent drop in the cost of jet fuel, the top 10 U.S. carriers made $6.2 billion more in the third quarter of last year than they did in the same period in 2014, reports the U.S. Department of Transportation. Naturally, they've responded to this crippling cash inflow by hiking ticket prices, because, uh, hmm.

Delta Airlines started the trend this Monday, announcing a fare increase of up to $4 per flight, the L.A. Times reports. Southwest Airlines announced a similar hike later that day, while American, JetBlue, Virgin America, and United jacked up their prices on Tuesday.

It should be noted that the airline industry is currently under investigation by the U.S. Justice Department for collusion. (Did you know that the five airlines that hiked fares this week control 80 percent of the nation's travel market?) Though the carriers under scrutiny deny any wrongdoing, the government probe is combing through two years of records to discern whether the airlines illegally communicated to limit flight availability and keep prices high.