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Responding to this question there was some discussion on GPS equipment and whether it used augmentation (WAAS/SBAS/GBAS) or not. What percentage of airliners operate with unaugmented GPS equipment? Maybe restrict to US/Europe to simplify. It might be easier to identify certain sets of airliners which have augmented GPS, which I would consider responsive.

I found the FAA first authorized use of WAAS for instrument approaches in 2003, which was also when the first WAAS approaches were published.

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  • $\begingroup$ A SBAS delivers corrections and satellite integrity data, but only for a region, and only for some constellations. WAAS is the SBAS providing GPS augmentation over the North America region. Another SBAS must be used when operating with GPS in another region (e.g. EGNOS when operating in Europe) or when using another constellation (e.g. EGNOS provides augmentation over Europe both for GPS and Galileo). $\endgroup$
    – mins
    Commented Nov 4 at 11:55

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In the US, this is rapidly in flux. There's an effective FAA ADS-B Out requirement for SBAS or multi-frequency/multi-constellation. It was supposed to take effect January 1, 2020, but there's exemptions out to December 31, 2024. After that date, it should be pretty close to "none".

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  • $\begingroup$ Both sources you linked say "WAAS is not required", you just need "adequate accuracy (within 0.05 NM)". Do you have a source that actually shows most airliners in US airspace have an SBAS receiver installed? $\endgroup$
    – Bianfable
    Commented Jun 7 at 6:51
  • $\begingroup$ @Bianfable You misunderstand. Read the first link again. It says WAAS is not explicitly required but it is the only technology at this time that meets the requirements. Any other receivers, like GPS L5 and GPS+Galileo would include WAAS anyway. $\endgroup$
    – user71659
    Commented Jun 7 at 16:18
  • $\begingroup$ I read that sentence as: with WAAS you meet these requirements >99.9% of the time, without WAAS you might meet these requirements at less than 99.9% of the time, but are allowed to fly. So an aircraft without WAAS would be allowed to operate as long as uncorrected GPS is currently accurate enough. $\endgroup$
    – Bianfable
    Commented Jun 7 at 16:43
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    $\begingroup$ @Bianfable Nope. Read the next paragraph. What WAAS is needed for is integrity data. With unaided GPS, there is no guarantee that 99.9% of the time your transmitted position is correct due to the risk of a GPS fault. Obviously, failures cannot be predicted ahead of time. "An aircraft that is not equipped to meet the requirements of this rule will not have access to the airspace for which ADS-B is required." $\endgroup$
    – user71659
    Commented Jun 7 at 16:52
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    $\begingroup$ @Bianfable Other sources: Textron "ADS-B will require at least one Wide Area Augmentation System (WAAS)-capable GPS receiver connected directly to the transponders." AOPA "Two things are required for ADS-B Out capability: an approved position source—generally a Wide Area Augmentation System (WAAS)-approved GPS receiver—and an ADS-B transceiver." $\endgroup$
    – user71659
    Commented Jun 7 at 16:57

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