From the Seattle Times today:
As fog shrouded Paine Field in Everett Monday, Alaska Air regional carrier Horizon Air was forced to cancel all commercial flights in and out of the airfield because of limitations on low visibility flying imposed to avoid 5G interference.
Horizon is currently the sole airline operating commercial flights out of Paine Field and all those are flown on the Embraer E175, a 76-seat regional jet.
The limitations imposed by the Federal Aviation Administration to prevent interference with cockpit instruments have created a problem specific to that aircraft and certain airports, including Paine Field and Portland International Airport.
And further
Whether the FAA granted clearance depended on what model of altimeter was installed on each aircraft and also how close the cell towers at each airport were to the runways.
The altimeters on Horizon’s Q400 turboprop planes — supplied by Collins — allowed those aircraft to be cleared everywhere. But Sprague said that the specific Honeywell altimeter on the E175 jet required airport-specific limitations.
“The configuration of the Honeywell radio altimeter in the E175, and how it integrates with the other aircraft systems on the E175, are such that the the likelihood of interference from the 5G signal is greater,” said Sprague.
The FAA therefore cleared the E175 to use only runways further away from the cell towers.