The carriage of Mode S and ADS-B equipment applies to State aircraft operating in European airspace on the basis of obligations defined in the National context and/or in the sequence of SES regulatory initiatives.
The performance and interoperability requirements related with the carriage of Mode S (ELS and EHS) and ADS-B OUT in European Union airspace, for flights under GAT/IFR status, are regulated by the Commission Regulation (EU) No 1207/2011 (SPI IR3 ) amended by Regulation (EU) 2020/587 of 29 April 2020.
Article 8 of the SPI IR mandates, from 07 December 2020, the carriage of Mode S ELS for all State aircraft and Mode S EHS and ADS-B OUT for Transport type State aircraft when operating as GAT/IFR. Article 8 applies only to EU State aircraft, thus non-EU State aircraft are not covered by that Article 8 (nor by the SPI IR).
For EU State aircraft, Member States had until 1 January 2019 to communicate to the European Commission which State aircraft cannot be equipped with the Mode S or ADS-B OUT capabilities as per Article 8.3 of the SPI IR. Such exemptions were limited to three reasons justifying non-equipage, in Article 8(3) of Regulation (EU) No 1207/2011.
Non-EU State aircraft operators that plan to conduct flights with non-Mode S or non-ADS-B OUT transport type State aircraft in European airspace shall consult the National AIPs of the States to be overflown, and submit case by case requests for dispensation/waivers for such particular flights in line with arrangements and procedures published therein.
 State aircraft with a maximum certified take-off mass exceeding 5 700 kg or having a maximum cruising true airspeed capability greater than 250 knots. It applies for aircraft with an individual certificate of airworthiness first issued on or after 7 June 1995.
 As per SPI IR, transport-type state aircraft means: “fixed wing State aircraft that are designed for the purpose of transporting persons and/or cargo.”