Major airlines suffered financially throughout the COVID-19 pandemic, with Spirit Airlines making headlines throughout the past year for numerous issues, including periods of extended flight disruptions and widespread customer dissatisfaction.

Statistics from the U.S. Department of Transportation show the company had a particularly high amount of customer grievances last year with 13.25 complaints per 100,000 passengers from January through September. Spirit also tied with Frontier in the American Customer Satisfaction Index of the industry’s worst customer satisfaction ratings.

Even before Spirit’s beleaguered 2021, the company was hit hard by the pandemic. In 2020, it received $334 million in aid in the form of grants and loans from the Coronavirus Aid, Relief, and Economic Security Act (CARES), which was largely used to pay employees.

The company had initially stated the funds would help its payroll until September 30, 2020, but announced in July of that year that it was putting 20 to 30 percent of its employees on leave of absence in the fall.

The Motley Fool reported around that time that about 600 of the airline’s 2,500 pilots were to be furloughed. However, the pilots’ union reached a deal with the company at the end of August for some pilots to take a voluntary leave of absence or work on a reduced schedule to avoid layoffs.

Like all airlines during the pandemic, the company had issues with passengers regarding its mask mandates. The airline also experienced several unusual incidents, including in March of 2021 when one of its flights from Cleveland was diverted from its California destination to Colorado after a passenger allegedly tried to open one of the plane’s emergency doors during midflight.

The airline had an especially problematic stretch in the summer of 2021, beginning on August 1 with the cancellation of 40 percent of its flights. Because the company had not booked passengers on other airlines, many passengers were left stranded. A wave of negative publicity hit the company as frustrated travelers aired their grievances on social media.

A company statement at the time said, “We’re working around the clock to get back on track in the wake of some travel disruptions over the weekend due to a series of weather and operational challenges. We needed to make proactive cancellations to some flights across the network, but the majority of flights are still scheduled as planned.”

The flight disruptions carried on for days. On August 3, Spirit canceled 42 percent of its flights and 61 percent the following day. The company said in a statement to Newsweek at the time that system outages, poor weather and staffing shortages caused the flights to be scratched.

A spokesperson for the airline said refunds would be issued for travelers whose flights had been canceled, but by the fifth day of disrupted flights, frustrated customers began claiming on social media that they were given $50 flight credits and meal vouchers after they were left stranded at airports.

During its worst period of flight disruptions, the airline canceled over 2,800 flights between July 30 and August 9.

The 2021 holiday season was difficult for the entire airline industry with around 8,000 flight cancellations happening. Reports of unruly passengers and staff shortages amid the rise of the Omicron variant also plagued the industry.

In order to ease the burdens put upon its staff, Spirit Airlines made the costly decision to double the pay of its flight attendants.

“All flight attendants, regardless of how you have obtained your pairing, will be receiving 200% pay for any pairing that touches Dec. 28 through Jan. 4,” the Association of Flight Attendants-CWA (AFA), the union representing Spirit, said in a statement shared with Reuters.

News of Frontier’s deal for Spirit comes as the latter airline reported a 2021 loss of $440.6 million, which was better than the $719.6 million loss it experienced in 2020.

Spirit CEO Ted Christie claimed in a Monday statement that its deal with Frontier Holdings Inc. would bring about positive measures. He said the “transaction is centered around creating an aggressive ultra-low fare competitor to serve our guests even better, expand career opportunities for our team members and increase competitive pressure, resulting in more consumer-friendly fares for the flying public.”