In the years since Hurricane Katrina ravaged New Orleans, the 911 system had undergone a major overhaul. The aging telephone system was replaced. Separate centers for medical, police and fire calls were consolidated under one roof. And new call-routing technology to prevent the whole thing from going down during a disaster was scheduled to be installed early next year.

Then Hurricane Ida hit, and the 911 call center crashed, failing its first major test.

Calls for help didn’t go through. The center was offline for 13 hours on Monday. The Orleans Parish Communication District, which runs the dispatch center, was forced to take to Facebook to tell people that if they had an emergency, they should walk to a nearby fire station or flag down a police officer to report it.

“Our technology is antiquated,” Tyrell Morris, the district’s executive director, said Monday.

Many of the problems that sealed New Orleans’ fate 16 years ago didn’t arise with Ida. The rehabilitated levee system largely held back the storm surge, and the pumps that drain excess water kept on working, despite the loss of electricity, powered by generators.

But emergency communications remained an issue.

The dispatch center’s new way of receiving 911 calls wasn’t ready. The district had signed a contract with AT&T for its ESInet online call-routing system last fall. But work on putting it in place is still months away.

AT&T also holds the contract for delivering emergency calls to the 911 center over landlines and through conventional switching stations. That old technology — vulnerable to flooding and power outages — failed.

“The calls never got to the building,” Morris said.

Police and fire officials were still able to talk with dispatchers and each other — their old radio transmissions were not affected.

AT&T’s basic cell service also came under criticism from New Orleans residents — and the family and friends trying to reach them, judged by looking at the deluge of complaints on social media. AT&T spokesman Jim Greer responded to questions about whether AT&T fared worse than other carriers after Ida by writing in an email: “I’m not sure that is the case.”

AT&T said 60 percent of its wireless network in Louisiana was working normally early Monday — rising to 82 percent later in the day as crews worked to restore service. Verizon said it was seeing only limited problems. “We are pleased to date with performance of the network,” Verizon spokeswoman Karen Schulz said. T-Mobile reported its network was “about 70% operational across Louisiana and Alabama.”

Greer did not respond to follow-up questions about AT&T’s contract with the 911 center.

The failure of communications equipment during Ida highlights lessons learned during Hurricane Katrina. That storm knocked out 38 911-call centers in Louisiana, Mississippi and Alabama. More than 1,000 cellphone sites went down and an estimated 20 million telephone calls did not go through the day after Katrina hit, according to a later inquiry by the Federal Communications Commission. “The entire communications infrastructure on the Mississippi Gulf Coast was destroyed,” said a 2006 report from a special House bipartisan committee that investigated the response to Katrina.

“It is at times like these that we are reminded of the importance of being able to communicate,” then-FCC chairman Kevin Martin told the U.S. Senate Committee on Commerce, Science and Transportation in 2005.

After Katrina, the FCC set up an independent panel to examine the hurricane’s effect on local communications networks. It also sought to require cell service providers to keep up to eight hours of backup power at each cell site, but was forced to abandon that plan amid an industry lawsuit, according to the energy trade publication E&E News.

Service disruptions are not unusual during a hurricane. Widespread outages occurred following hurricanes Matthew in 2016, Harvey, Irma and Maria in 2017, and Florence and Michael in 2018.

Nationwide 911 service outages have happened, too. In August 2014, 50 million T-Mobile subscribers lost access to 911 service for three hours due to a technical error. Another incident in 2017 cut off 911 call access for five hours for 135 million AT&T subscribers.

But the loss of cell service in the wake of a hurricane had special resonance in a city still recovering from Katrina.

Complaints about people not being able to reach family and friends in the hurricane zone flooded onto Facebook and Twitter — two services that weren’t available to the general public when Katrina struck in 2005.

“Calls are impossible, for the most part, but texts and some apps appear to work,” tweeted one person. A woman trying to check on her family in New Orleans wrote they “managed to get a single text message through to say they’re fine — cellphone service is very limited though, so people may not check in for a while.”

Many complaints seemed to single out AT&T’s cell service for criticism. “Do better @ATT!” tweeted one person in Oregon. “I have reached every person in New Orleans who has Verizon. My mother is completely unreachable as well as friends who have @ATT. No one knows if any of them are safe!”

A reporter for the Baton Rouge Advocate noted in a tweet that problems with AT&T’s cell service reminded her that her newspaper “switched us to Verizon after this happened during 2016 BR [Baton Rouge] floods.”

Some people posted phone numbers for official parish emergency contacts, while many others directed them to the voice mail line for the Cajun Navy, a volunteer boat brigade that has helped rescue stranded people during major floods and hurricanes.

The Cajun Navy’s Facebook page Monday morning advised volunteer boat-owners to report to a nearby Days Inn to assist with water rescues and the chain saw teams working on the removal of road debris. They also advised volunteers to chat over the walkie-talkie app Zello, which allows push-to-talk communications for big groups over cell networks and has been used by volunteer rescue teams during other recent natural disasters.

Many people turned to the group’s Facebook page for help. One woman wrote on Facebook that her mother, who couldn’t get home due to a tree blocking roads in her neighborhood, had been at an Exxon station “at 130am with no power. Haven’t heard from her since. Her phone provider is out and no wifi without power.”

Another woman wrote on Facebook Monday morning, “Please dont forget my mom in Folsom. I can’t get ahold of her or my sister’s … thankyou with all my heart.”

Morris said other parishes also saw their 911 systems go down during Ida thanks to old equipment. AT&T is the provider for all 911 centers in Louisiana, he said.

Orleans Parish, home to New Orleans, will be among the first in the state to use the new call-routing technology.

As to why it hadn’t been installed years ago, Morris said part of the reason was, “It’s expensive.”