A barometric altimeter and altitude reporting transponder are self contained units with separate determination of altitude based on pressure. The source in comm

A barometric altimeter and altitude reporting transponder are self contained units with separate determination of altitude based on pressure. The source in common they share is the static (pressure) system. In the case of this flight, maintenance tape covered the static ports, rendering all instruments that use the static pressure system, significantly in error. Although there's more than one port, and thus redundancy, the maintenance operation covered all of the ports.