Southwest Airlines’ increasingly acrimonious public feud with minority shareholder Elliot Investment Management has heated up a notch just days before the carrier is scheduled to update investors on its strategy.

The private equity firm, which now holds 11% of the Dallas-headquartered airline’s outstanding shares, early on 25 September published a strongly worded letter to fellow investors accusing the Southwest board of incompetence.

It calls for a special investor meeting in the coming weeks to “make you aware of certain defensive actions that Southwest’s leaders are taking, apparently in an attempt to disenfranchise shareholders and evade accountability for their poor performance”.

Elliot, based in West Palm Beach, Florida, says the carrier’s management and board have made “a chaotic series of defensive actions”, and chose ”a go-it-alone path with the goal of obstructing a leadership change that is urgently needed”. It calls the airline’s announcement of recent changes in an attempt to return to profitability “half-baked”.

”Now we are seeing reports that Southwest executives are warning employees of ‘difficult decisions’ ahead that could adversely affect workers, which are supposedly being made in response to demands from Elliott Management,” the company says.

”Whatever ‘difficult decisions’ management have decided must be made, they are the product of a failed management team that has delivered years of deteriorating performance and is now taking any action – no matter how short-sighted – that they believe will preserve their own jobs.”

Southwest Airlines wasted no time in responding to the letter. It says it has attempted to “reach a constructive resolution” with Elliott in recent weeks, but that the investor has “remained entrenched” in its position.

These attempts include “over a dozen phone calls with Elliott representatives, several in-person meetings and an offer for Elliott to participate in the company’s board refreshment process and understand its views on Southwest’s business and strategy”, Southwest says.

“It’s unfortunate that Elliott has not only completely failed to engage constructively, but today has continued its pattern of launching public ambushes and is seeking to disrupt Southwest’s upcoming investor day,” the company adds.

Southwest plans to hold its investor day in Dallas on 26 September.

Earlier this month, Southwest announced changes to its 15-member board of directors, in an attempt to assuage the pressure coming from Elliott. Six directors will retire in November, while executive chairman and former chief executive Gary Kelly will retire next year. The airline also brought in long-time industry executive Rakesh Gangwal, co-founder of India’s InterGlobe Aviation, which operates under the IndiGo airline brand.

The six resigning directors are David Biegler, Veronica Biggins, US Senator Roy Blunt, William Cunningham, Thomas Gilligan and Jill Soltau. Southwest expects the board to be reduced to 13 members following the exodus. In July, it adopted a strategy aimed at fending off Elliott when it approved a rights plan that lets stockholders buy shares at a 50% discount should any entity acquire at least 12.5% of the stock.

At the time, Southwest’s board reiterated its continuing support of current chief Bob Jordan, maintaining that it is “confident that there is no better leader… to successfully execute Southwest Airlines’ robust strategy to evolve the airline and enhance sustainable shareholder value”.

In addition, in July, Southwest said it will abandon its open-seating policy and add more extended-legroom seats for sale at a premium.

Elliot has called these changes “too little, too late”.

Elliot, for its part, in August put forward a slate of its own board nominees, which include former airline chiefs David Cush and Gregg Saretsky, to replace the incumbents, which it sees as “profoundly out of touch” with investors following a series of blunders earlier this year.

Southwest had long been among the USA’s most-profitable airlines – universally known for eschewing baggage and reservation change fees and for pioneering a low-cost-carrier model that numerous airlines have since emulated. But it has stumbled of late, rattled by increased competition, including from newer “ultra-low-cost” carriers like Frontier Airlines and from “basic” economy tickets offered by major carriers. Southwest has also been hamstrung by significant delays from Boeing in delivering new 737 Max jets.

“The urgency of management and board change at Southwest could not be clearer,” Elliot writes in its most recent attack on Southwest’s management. “In the coming weeks, we will be formally requesting a special meeting to provide you with a choice between the new directors that we have put forward – who we believe possess the qualifications and skills to guide Southwest to a brighter future – or a board that lacks relevant expertise and has pre-committed itself to supporting failed CEO Bob Jordan.”

Southwest’s net profit fell 46% in the April-June period to $367 million. Operating profit was down 50% at $398 million on revenue up 5% at $7.5 billion. It will publish third-quarter results in mid-October.