(NewsNation) — Thousands of passengers were left stranded or scrambling for new flights as Southwest Airlines melted down during the winter storm that hit the country over Christmas, and the president of the Southwest Pilots Association said employees have been warning about the possibility for years.

Winter weather impacted flights across all airlines, but Southwest has struggled to recover even as other carriers have begun to return to normal. The airline has continued to cancel thousands of flights and is being investigated by the Department of Transportation for an “unacceptable” rate of cancellations.

Southwest Pilots Association President Capt. Casey Murray said the meltdown has been devastating for the frontline employees who are left dealing with upset travelers.

“We’re extremely sorry, to our customers who are stranded who who’ve lost time who’ve lost, you know, memories with their family,” he said.

Murray blamed the problem on mismanagement and outdated systems. Murray said Southwest hasn’t updated some processes since the 1990s despite employees warning something like this could happen.

“On a podcast I said I fear that we’re one thunderstorm, one ATC event, one brown out away from a complete meltdown. Whether that’s Thanksgiving, Christmas or New Year’s, that’s the precarious situation we’re in,” he said. “Now we’re living it.”

Murray acknowledged that scheduling and monitoring a major airline is a very complex process. But he said it didn’t have to wind up the way it has for Southwest.

“But again, if you look at Denver, on Christmas Eve, United, about the same size [as Southwest]. We are in Denver, dealt with the same storm, same precipitation, same winds and they didn’t have near the cancellations and delays we did,” Murray said.

In addition to fixing the problems that caused Southwest to cancel so many flights, Murray said it’s critical the company make things right for customers who had to scrap holiday plans or shell out extra money to rebook tickets.

“We can’t move forward until we make up for the failure that occurred and with our passengers. They are really what we rely on,” Murray said.