U.S. airlines are asking shareholders to believe they can raise ticket prices while ramping up the supply of seats. To Wall Street, that sounds like a fairy tale.

Six attempts at broad-based fare increases have failed in the last two months, most recently a bid last week by Delta Air Lines Inc (DAL.N) The last successful widespread price hike was Oct. 10, said JPMorgan Chase & Co. analyst Jamie Baker, even as oil prices rebounded from a three-year slump.

That’s creating a confidence crisis for investors, who last week sent airlines to the biggest drop since 2015 when United Continental Holdings Inc. (UAL.N) announced an aggressive expansion plan. The No. 3 U.S. carrier is hardly alone. Southwest Airlines Co., JetBlue Airways Corp. and Alaska Air Group Inc. are also planning to grow faster than the economy.

The worry is that the only way to generate enough demand to fill the new seats is by cutting prices. And that risks triggering fresh fare wars just as profits are under pressure from rising fuel costs.

“Capacity is starting to increase faster than demand,” said Samuel Engel, senior vice president at consultant ICF. “At that point any one carrier starts to say, ‘I’d rather add capacity and try to steal share than support a fare increase across the industry.’”

A Standard & Poor’s airline index is still 10 per cent lower than before United disclosed its growth plans. The gauge fell 2.7 per cent at the close in New York.

FARE WARS

It’s a competitive business, and one carrier’s attempt to raise fares can be another’s opportunity to win new customers with bargain prices. But one reason investors including Warren Buffett have bought airline shares is the expectation that after years of industry consolidation, carriers will be able to maintain steady profits, thanks in part to stronger pricing power.

Delta and American Airlines Group Inc. (AAL.O), the two biggest carriers, have slowed their expansion in recent years to let demand catch up with supply — and make it easier to charge more for tickets. They’re only boosting capacity 2.5 per cent this year, roughly in line with growth expectations for gross domestic product, a barometer of travel demand.

A slower seat expansion helped defuse fare wars that began in 2015 and flared up again last summer before subsiding later in the year. And with the improving economy, it’s possible airlines will still be able to boost passenger revenue for each seat flown a mile, a proxy for pricing power, despite all the capacity growth.

“We think the fare environment will be strong enough to offset higher-than-expected capacity growth out of United,” David Vernon, an analyst at Sanford C. Bernstein & Co., said in a note Wednesday. “The fare environment will surprise to the upside against now lower expectations through the first three quarters of 2018.”

SUPPLY GROWTH

But a fast-growing supply of seats will be a headwind for efforts to raise fares. United reignited concern last week with its plan to expand as much as 6 per cent each year through 2020. JetBlue said it would boost 2018 capacity as much as 8.5 per cent, Alaska Air has targeted 7.5 per cent and Southwest will grow about 5 per cent.

Total industry capacity will increase about 5.5 per cent, said George Ferguson, a Bloomberg Intelligence analyst.

For now, “Airlines don’t have pricing power,” he said. It will be difficult for carriers to raise fares this year enough to offset the higher cost of fuel, “unless somebody modifies their expansion plans, especially United and Southwest.”

Southwest, which pioneered the discount model, is a frequent holdout from rivals’ attempts to raise fares. United didn’t match a Delta price increase last month, JPMorgan’s Baker said. The attempt later failed.

RISING COSTS

Deep discounter Spirit Airlines Inc. and other smaller carriers should be eager to see fares climb as they face higher labor and fuel prices, said Andrew Davis, an analyst at T. Rowe Price Group, the largest shareholder at American, and an investor in United, Delta and Southwest. The price of fuel in New York has risen above $2 a gallon, about 30 per cent higher than a year ago.

Doug Parker, chief executive officer of American, said Jan. 25 that fares “are too low for oil prices this high.” Carriers will find a way to pass on the increase to consumers, he said, “but it takes time.”

There’s generally a gap of at least three months between when fuel climbs and fare increases show up.

POWER VACUUM

Historically, airlines have dealt with rising fuel prices by paring back capacity, Delta CEO Ed Bastian said last month. It’s too early for Delta to think about adjusting its growth plans, but the carrier will be prepared to act if fuel prices “continue on this tear,” he said.

Carriers are right to be cautious about raising fares too quickly, said Rick Seaney, chief executive of 3 Victors, which tracks real-time air fare purchases. There’s a risk that when ticket prices increase enough to cover the cost of fuel, that can also discourage some travel.

“Of the 2 million passengers flying on a given day, 1 per cent to 3 per cent may not have taken that trip had the price been $1 or $3 more,” Seaney said. “Each one of those passengers had a breaking point where they wouldn’t have flown. One more dollar and you broke the camel’s back."