Alaska Airlines already tried to shore up its IT infrastructure after an outage in July forced the Seattle-based company to ground flights across the country.

Apparently, it wasn’t enough.

Alaska was hit with another major outage on Thursday, leading to a ground stop that lasted eight hours and resulted in more than 400 flights canceled across Alaska Airlines and its subsidiary Horizon Air.

In a new update Friday afternoon, the company said more than 49,000 passengers had their travel plans disrupted.

The outage was severe enough to postpone the company’s scheduled quarterly earnings call Friday. Shares were down more than 6%.

Alaska said it was still working to normalize operations.

The company has blamed the outage on a failure at its primary data center. It was not due to a cybersecurity incident.

“Following a similar disruption earlier this year, we took action to harden our systems, but this failure underscores the work that remains to be done to ensure system stability,” the company said in its latest update. “We are immediately bringing in outside technical experts to diagnose our entire IT infrastructure to ensure we are as resilient as we need to be. ”

It added: “The reliability of our technology is fundamental to our ability to serve guests and get them to where they need to be.”

Alaska said its July outage was caused by a failure of a “critical piece of hardware” at its data centers.

The airline operates a hybrid infrastructure, blending its own data centers with third-party cloud platforms, according to an interview last year with Vikram Baskaran, Alaska’s vice president of IT.

Alaska began migrating workloads to Microsoft Azure around 2015 and continues to maintain its own data centers for critical workloads, according to the interview.

The company last year partnered with Google Cloud on a generative AI-powered search experience.

The impact of this week’s outage was evident at Sea-Tac Airport on Thursday evening, where long lines wrapped around the concourse and a maze of suitcases piled up in the baggage claim area.

Alaska said Friday it does not have an estimate of the financial impact of the outage. The company’s Hawaiian Airlines subsidiary was not affected.

Alaska said the July outage was expected to reduce earnings by about $0.10 per share, or roughly $12 million.

The company on Thursday reported third quarter revenue of $3.8 billion, up 1.4% year-over-year, while profit dropped 69% to $123 million.