Business travel is taking off, providing major airlines with a much-needed lift.

The year is off to a "very strong start, but in particular, business volumes have gotten off, and are just really compelling," United Airlines Chief Commercial Officer Andrew Nocella said during a conference call after the carrier released its quarterly results this week, according to a transcript made available by AlphaSense.

United said that corporate ticket sales are a high-single-digit percentage above where they were a year ago. Nocella said this "pretty amazing" business demand is expected to continue, factoring into the company's forecast that earnings in the first quarter will rise 37% versus last year.

The increase in business travel has been playing out across the industry as companies prioritize in-person meetings, said Frank Holmes, CEO of U.S. Global Investors, Inc., an investment manager and advisor. "Business travel is coming back at a steady pace across many of the carriers," he said in an email.

It's a welcome development for airlines that have had to rely on international travel and premium ticket sales to drive growth while main cabin ticket sales slump as less-affluent consumers pull back. Shares of United and Delta Air Lines (DAL) have risen about 4% over the past 12 months, significantly lagging the performance of the S&P 500, while American Airlines (AAL) stock has shed nearly 20% of its value in the past year.

Main cabin sales are still lagging, United said. Revenue rose 1% year-over-year last quarter in the main cabin, while capacity was up 6%, Nocella said. Premium cabin revenue increased 12% year-over-year, with capacity up 7%, he said.

United, like Delta, has been surprised at how slow the industry has been to curb main cabin capacity, which is not always profitable for carriers. At some point, there will be fewer main cabin seats and less pressure to fill them at a loss, Nocella said.

"I can't predict the [timing], but I do think eventually businesses stop doing unprofitable things," he said, per the transcript. "I remain bullish that we are going to see the performance of the main cabin flip at some point in the future. And when it does, that will be enormous fuel to our margin growth and be great for the industry."