According to the FAA, “certain aircraft equipped with the Rockwell Collins GPS 4000-100 and select ADS-B out GPS receivers are indicating ‘ADS-B fail, unavailable, TCAS fail or transponder fail’ messages.”
Aircraft without working transponders were directed to coordinate with the FAA before departure, a prior directive had instructed those planes not to fly above 28,000 feet.
Rockwell Collins, acquired by United Technologies last year, provides avionics and information technology systems and services.
The issue appears to center on some of the company’s ADS-B (Automatic Dependent Surveillance-Broadcast) systems that send flight data to be picked up by ground stations.
Whether the issue was caused by poor GPS data or a software upgrade to affected systems remains speculation, nothing has yet been confirmed.
According to CNBC, regional carriers in the U.S. “canceled about 400 flights scheduled for Sunday.” A Delta spokeswoman said “about 80 of its regional flights were canceled,” and American and United regional carriers were hit by the same issue.