JUNE 28, 2026
A network of 15 ground stations across India measures GPS errors and beams the corrections up to satellites over the equator. (Photo: PTI)
On the afternoon of June 27, 2026, an IndiGo Airbus A320 dropped gently towards the runway at Udaipur. From a window seat, nothing looked unusual.
Yet the aircraft was not being guided down by the ground-based radio beams that line most big-city runways.
It was being talked down by satellites parked thousands of kilometres above India, media reports said.
Under the watch of the Directorate General of Civil Aviation (DGCA), it became the first jet in India to land using Gagan, the country’s own homegrown navigation system.
Small turboprop planes had managed it before. A passenger jet never had.
A turboprop is a smaller, slower aircraft powered by a propeller that is spun by a jet engine, the kind used on short regional routes, such as IndiGo’s ATR fleet, rather than the larger jets like the A320 that fly busier sectors.
WHAT IS GAGAN, AND WHO BUILT IT?
Gagan stands for GPS Aided GEO Augmented Navigation. It was built jointly by the Indian Space Research Organisation (Isro) and the Airports Authority of India (AAI).
The Gagan Signal-In-Space (SIS) is available through Isro’s GSAT-8 and GSAT-10.
An IndiGo Airbus A320 on final approach to Udaipur on June 27, 2026, guided down by GAGAN, India’s own satellite navigation system. (Representative Photo of an IndiGo Airbus: PTI)
WHY IS LANDING A PLANE WITH GPS SO HARD?
The GPS in your phone is usually accurate to a few metres.
That is fine for finding a coffee shop. It is nowhere near sharp enough to bring a 70-tonne jet down through clouds.
Gagan was developed jointly by Isro and the Airports Authority of India to sharpen GPS signals for aviation use. (Representative Photo of an IndiGo Airbus: PTI)
As GPS signals travel to Earth, they are slowed and bent by the ionosphere, an electrically charged layer of the upper atmosphere.
Over India, which sits beneath a restless band called the equatorial ionisation anomaly, those errors are unusually large and shift from minute to minute.
HOW DOES GAGAN FIX GPS ERRORS?
A network of 15 ground stations across India, whose exact positions are known to the centimetre, constantly compares where GPS thinks they are with where they truly are. That gap is the error.
A control centre calculates the correction, beams it up to satellites hovering over the equator, and those satellites broadcast it straight back down to the aircraft.
GPS signals are bent and slowed as they pass through the ionosphere, the charged upper layer of the atmosphere above India. (Representative Photo of an IndiGo Airbus: PTI)
The plane’s receiver applies the fix.
Just as importantly, it is told how much to trust the answer, and if the signal cannot be trusted, the system warns the pilot within seconds.
WHY DOES THE UDAIPUR LANDING MATTER?
The flight flew what is called an LPV approach, short for Localiser Performance with Vertical Guidance.
In plain language, it hands the pilot both left-right and up-down guidance to the runway, much like the costly ground-based Instrument Landing System (ILS), but without a single piece of equipment at the airport itself.
An LPV approach gives pilots ILS-style guidance to the runway without any costly ground equipment at the airport. (Representative Photo of IndiGo Airbuses: PTI)
That is the real prize. Fitting ILS into every small airport is expensive. Gagan offers the same precise, ILS-style descent using a system that already exists in orbit.
For a country building regional airports at speed, that means safer landings in poor weather, fewer diversions and lower costs. India is one of only a handful of nations with such a system, and the only one proven over the difficult equatorial sky.
Courtesy: India today / PTI
