Earlier quoted context omitted.
Highly dependent on weather and the complexity of the approach. Clear skies and VFR? I would agree. Heavy weather and an instrument approach or confounding factors? Not accurate imho. > At midnight on May 14, eight minutes after Clark and Kawsara took off from Roswell, they told Albuquerque Center that they’d lost their GPS. Unable to navigate on their own, they asked that the controller give them a heading—a magneti…
GPS is not, and never will be, reliable enough for IFR on its own. Relying on a tower in instrument conditions because GPS failed is unacceptable, because every other GPS user is in the same boat. If you’re flying IFR, you should have a working set of instruments and be using them. Why didn’t these pilots have their VORs tuned in for positioning?
WAAS GPS (~7.6M accuracy) is reliable enough for IFR on its own that many approaches have removed legacy RF ILS equipment for instrument approaches (RNAV LPV with synthetic glidescope from GNSS). I would agree this does not apply to the vast majority of general aviation (although certified receivers supporting this are well within the reach of GA at ~$6k), but facts and specifics are important, so enumerating that GPS and these trimmings make it designed to replace traditional IFR equipment under certain circumstances. WAAS is not a paid service, the additional precision is free if your receiver and autopilot supports it.
Further reading:
https://www.faa.gov/about/office_org/headquarters_offices/at...
https://www.aopa.org/news-and-media/all-news/2025/october/pi... ("Today most IFR pilots use GPS as a primary source of navigation, whether they’re flying a departure, airway, or arrival defined by VORs; or segments of approaches based on navaids or that require DME or ADF.") [My note: This is straight from the advocacy group for general aviation in the US, AOPA.]
https://www.flyingmag.com/everything-you-need-to-know-about-...
https://boltflight.com/loc-vs-ils-vs-gps-approach-understand...
https://www.faa.gov/air_traffic/publications/atpubs/aim_html...
https://en.wikipedia.org/wiki/Wide_Area_Augmentation_System
> "The Wide Area Augmentation System (WAAS) is an air navigation aid developed by the Federal Aviation Administration to augment the Global Positioning System (GPS), with the goal of improving its accuracy, integrity, and availability. Essentially, WAAS is intended to enable aircraft to rely on GPS for all phases of flight, including approaches with vertical guidance to any airport within its coverage area. It may be further enhanced with the local-area augmentation system (LAAS) also known by the preferred ICAO term ground-based augmentation system (GBAS) in critical areas."
> In 2007, WAAS vertical guidance was projected to be available nearly all the time (greater than 99%), and its coverage encompasses the full continental U.S., most of Alaska, northern Mexico, and southern Canada. At that time, the accuracy of WAAS would meet or exceed the requirements for Category 1 ILS approaches, namely, three-dimensional position information down to 200 feet (60 m) above touchdown zone elevation.
Category II or III ILS GPS approaches are supported when the subject airport has a local reference station reporting corrections ("LAAS"). With enough precision, the aircraft can land itself with GPS and local corrections ("Autoland"). A King Air running Garmin's SafeReturn recently performed this autonomously with GPS alone (to the best of my knowledge).
https://en.wikipedia.org/wiki/Local-area_augmentation_system
https://www.faa.gov/airports/planning_capacity/non_federal/g...
Autoland saves King Air, everyone reported safe - https://news.ycombinator.com/item?id=46346214 - December 2025 (185 comments)
Event ATC recording: https://www.youtube.com/watch?v=K3Nl3LOZNjc