From the air, the devastation Hurricane Maria brought to Puerto Rico appears to be catastrophic.

SAN JUAN, Puerto Rico — Double-barreled hurricanes that wiped out the island’s cellphone towers have left 91% of Puerto Rico without cellphone coverage, cutting off a lifeline to family and first responders.

The extraordinary lack of connectivity, further hampered by electricity outages and fuel shortages, has led to several low-tech solutions — some people are using AM radio stations to send over-the-air messages.

As the major U.S. cellphone carriers send in personnel and supplies to rebuild destroyed networks, one stopgap solution has emerged: a program that relays the most basic of information, that an individual’s cellphone has been turned on and connected. 

AT&T and T-Mobile, two of the four biggest carriers in the U.S. territory, have for the first time created programs that allow people in the United States to register the cellphone number of family or friends in Puerto Rico, regardless of the carrier of the person registering.

When the Puerto Rican customer’s cellphone is first able to connect to a network, they will immediately be notified that family and friends in the United States are trying to contact them.

As of Thursday, more than 12,250 people had signed up on AT&T’s website for the service.

The wait could be a long one. According to the Federal Communications Commission, as of Thursday, 31 of Puerto Rico’s 78 municipalities had no functioning cell sites at all. Across the U.S. territory, 75% of cell sites are currently out of service.

The widespread destruction of the infrastructure that makes modern, connected life possible is worst outside the capital, San Juan, but even there cellphone hot spots are few and far between.

According to the FCC, of the area’s 364 cell service towers, 284 were out of commission Thursday.

Cellphone service was extremely limited but occasionally available in odd spots along highways around Puerto Rico.  

Each day, on Highway 22, just west of San Juan, motorists parked their cars on the shoulder of the highway and congregated on the sides of the…