The Federal Aviation Administration (FAA) has put forward a notice of proposed rulemaking (NPRM) that gives airlines an additional year, until February 1, 2024, to address faulty altimeters in their aircraft.    These altimeters, which measure an airplane’s height above the earth’s surface, are present on 7,993 planes registered in the United States. The FAA believes that 180 of these altimeters will need to be completely replaced, while 820 will need filters added to comply with the proposed modification requirement. This upgrade is expected to cost a total of $26 million.   The ruling is part of a settlement reached between the aviation and cellular sectors after AT&T and Verizon paid $69 billion for C-Band spectrum licenses. Airplane altimeters typically operate in the 4.2 – 4.4 GHz frequency, but certain altimeters cannot filter out 5G signals from the carriers’ spectrum in the 3.7-3.98 GHz range.   The FAA is therefore…