AT&T and Verizon have given the Federal Aviation Administration another year to fix altimeter issues as they look to roll out C-band 5G services around airports. “We believe we have identified a path that will continue to enable aviation and 5G C-band wireless to safely co-exist,” acting FAA administrator Billy Nolen said in a statement.

Under a phased plan, operators of regional aircraft with radio altimeters that are most susceptible to interference are required to fit them with radio frequency filters by the end of this year. That work is underway and the FAA says it will continue on an expedited basis.

The agency also says it worked with AT&T and Verizon to identify airports where they can bolster service with minimal risk of upending flight schedules. The FAA plans to monitor the pace of RF filter retrofits on altimeters too.

Altimeters have been at the heart of the tussle over the rollout of C-band 5G around airports. Airlines have been worried that, because C-Band frequencies are close to ones used by some altimeters, they could create interference. That could cause a plane’s landing system to misinterpret the distance to the ground with potentially disastrous consequences.

In January, AT&T and Verizon agreed to delay activating C-band 5G towers around airports until July 5. They made the pledge just hours before switching on C-band 5G in other areas for the first time. The pair also agreed to create buffer zones around 50 airports.

Now, the carriers will continue with “some level of voluntary mitigations” for another year, until July 5th, 2023. “After that time, the wireless companies expect to operate their networks in urban areas with minimal restrictions,” the FAA said.

“Through close coordination with the FAA over the last several months, we have developed a more tailored approach to controlling signal strength around runways that allows us to activate more towers and increase signal strength,” an AT&T spokesperson said. “Though our FCC licenses allow us to fully deploy much-needed C-Band spectrum right now, we have chosen in good faith to implement these more tailored precautionary measures so that airlines have additional time to retrofit equipment. We appreciate the FAA’s support of this approach, and we will continue to work with the aviation community as we move toward the expiration of all such voluntary measures by next summer.”

“Today’s announcement identifies a path forward that will enable Verizon to make full use of our C-Band spectrum for 5G around airports on an accelerated and defined schedule,” Verizon executive vice-president and chief administrative officer Craig Silliman said. “Under this agreement reached with the FAA, we will lift the voluntary limitations on our 5G network deployment around airports in a staged approach over the coming months meaning even more consumers and businesses will benefit from the tremendous capabilities of 5G technology. This progress is the result of months of close collaboration with the FAA, FCC and aviation industry, and sets the stage for continued, robust 5G deployment.”