Shares of airlines aren't having a good summer.

Since July 7, when it reached an all-time high, the Standard and Poor's Composite Airlines Index has fallen 17%. Of the eight major airlines, only Southwest Airlines Co. (LUV) has a year-to-date share price gain with its shares are up 5%.

The industry may get a chance to explain itself and perhaps reduce guidance this week. Key events include Delta Air Lines Co.'s (DAL) August traffic report, scheduled for Tuesday, Sept. 5; and the Cowen & Co. airline investor conference on Wednesday, Sept. 6.

With United Continental Holdings Inc.'s  (UAL)  chief financial officer in the spotlight after Hurricane Harvey struck Houston, the carrier's second-biggest hub, CFO Andrew Levy is scheduled to speak at the conference at 8:30 a.m. ET.

Cowen & Co. analyst Helane Becker wrote last Wednesday that she expects "managements will update guidance to the low end of the range" at the conference.

"Pricing trends are currently not favorable," Becker wrote. "Fares from the Northeast to Florida are again in double digits [and] walk-up fares in some markets are lower than advance purchase fares."

In particular, Becker said, walk-up fares in Denver, Newark and Chicago, are lower than expected. All three cities are United hubs where ultra-low-fare carriers have impacted pricing.

"If this continues into the December quarter, estimates will require another round of revisions," she said.

UBS analyst Darryl Genovesi also takes a dim view of industry prospects following an industry conference in Las Vegas last week.

"Domestic revenue trends have taken another leg down since initial Q3 guidance," Genovesi wrote in a recent report. He said most carriers may cut current third-quarter guidance.

Factors in the decline include efforts by United, American Airlines Group Inc. (AAL) and Southwest to match fare reductions by ultra-low-cost carriers Spirit Airlines Inc. (SAVE) and Frontier Airlines, geopolitical events and the impact of Hurricane Harvey, he said.

As for United, Becker has estimated that Harvey will have a $265 million impact on the airline, including lost revenue of $115 million and added cost of $150 million. CFRA Research analyst Jim Corridore estimated hundreds of millions in lost profits.

Standard & Poor's said last Thursday it sees no credit ratings impact on United. "The closest parallel may be Delta's 2016 information systems failure at its Atlanta hub that grounded traffic for three days and cost the airline about $150 million," the agency said.

The industry was sailing along until the Spirit second-quarter earnings call on July 27 spooked investors. On the call, Spirit executives said the carrier was facing competitive discounting, particularly at United hubs, possibly in retaliation for Spirit's fare cutting at Newark.

On that call, Matt Klein, Spirit's chief commercial officer, said the carrier has seen "a developing change in the pricing backdrop" that began in late June.

"The competitive environment has spread to a larger number of markets at deeper discount levels {as} our competitors resort to an unusual level of discounting," particularly for summer, Klein said. That day, Spirit shares fell 18%.

Year-to-date, Spirit shares are down 41%; Hawaiian Holdings Inc. (HA) is down 25%; Alaska Air Group Inc. (ALK) is down 15%: United is down 14% and JetBlue Airways Corp. (JBLU) is down 11%. Both American and Delta are down 3%.

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This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.

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