Air travel in the U.S. early Wednesday was disrupted by the failure of a key pilot notification system operated by the FAA. There was no estimate for the restoration of the Notice to Air Missions System and a hotline has been activated, the FAA said on its website. Publicly traded companies in the space include Alaska Air (ALK), American Airlines (AAL), Delta Air Lines (DAL), JetBlue (JBLU), Southwest (LUV), Spirit Airlines (SAVE) and United Airlines (UAL).