US airlines will be required to more than 1,000 next generation 737s with automated air data systems under an airworthiness directive to be published on 10 December.
The US Federal Aviation Administration has approved the directive 10 months after proposing the rule change.
The airlines operating the 737NGs will have 24 months to complete the changes estimates to cause $17,300 per aircraft or $17.7 million fleet-wide, the FAA says.
The agency increased its cost estimate from a total of $15 million after several carriers complained that was too low. The FAA added up to 30h of additional labour needed to remove and reinstall galleys and lavatories behind the cockpit to make the changes, as suggested by Southwest Airlines.
But the airlines failed to persuade the FAA to extend the timeframe from making the changes from 24 months to at least 30 months, despite arguments that the timing of the rule will require modifications outside of the heavy maintenance cycle.
The hardware change was initiated after three reports of pilots failing to manually activate air data sensor heating systems on 737NGs.
Air data sensors, which include pitot tubes, can provide incorrect or misleading information to the pilots if partially or fully blocked by ice.
The automated system will eliminate the risk of a "loss of control" event because the pilot neglected to manually activate the 737NG's air data de-icing system.