The FAA has mandated ADS-B Out capabilities for flight after January 1, 2020, for flight in most airspace where a Mode C transponder is required today. There is one significant exception: ADS-B also will be required in certain airspace above the Gulf of Mexico. Here are the specifics:
There is a graphical depiction and additional information on the FAA website.
At this time, only the United States is allowing the 978UAT datalink for ADS-B Out. If you plan to fly in ADS-B airspace outside of the United States, a 1090ES datalink—using a Mode S Extended Squitter transponder—will be required. Because the list of countries with ADS-B Out requirements and proposals is growing, we strongly recommend equipping with 1090ES if you plan to fly internationally. Remember that for countries without a mandate, there is no ADS-B Out requirement.
Australia. 1090ES required for all IFR operations. Foreign-registered aircraft equipped with transponders are exempted below FL290 until June 6, 2020.
Canada. Currently no mandate, but operators who voluntarily equip with 1090ES (particularly in the Hudson Bay and nearby oceanic airspace) can receive a higher level of service. Nav Canada is part of a joint air traffic surveillance venture, Aireon, installing ADS-B equipment on low-earth-orbit satellites. Nav Canada will be the launch customer when the service becomes available in 2018, and initially intends to incorporate 1090ES ADS-B into North Atlantic airspace.
Europe. 1090ES required for IFR aircraft with a MTOW exceeding 12,566 pounds or maximum cruise airspeed faster than 250 KTAS. Mandatory for new-production aircraft, and must be retrofitted into all aircraft by June 7, 2020. (Dates have slipped from original timetable.)
Hong Kong. 1090ES required in all airspace, FL290 and above.
Indonesia. 1090ES required, FL290 and above.
Mexico. 1090ES required beginning January 1, 2020, in Class A, B, C, E above 10,000 feet msl, and other specified airspace. Requirement effective now in Class E airspace over the Gulf of Mexico, at and above 3,000 feet msl within 12 nm of the Mexican coast.
Singapore. 1090ES required on specified airways.
Sri Lanka. 1090ES required within the Colombo Terminal Control Area (TMA), FL290 and above.
Taiwan. 1090ES required in all airspace, FL290 and above.
Vietnam. 1090ES required on specified airways.