Why IndiGo's Gagan-assisted landing is a milestone for Indian aviation

On June 27, an IndiGo Airbus A320 completed what appeared to be a routine landing at Udaipur Airport. Behind the scenes, however, the flight marked a significant milestone for Indian aviation. Instead of depending on conventional ground-based radio navigation equipment, the aircraft relied on Gagan, India's indigenous satellite-based navigation augmentation system, to guide its approach.

According to the Directorate General of Civil Aviation (DGCA), this was the first time a full-sized commercial passenger jet in India had completed a landing using the homegrown technology. While smaller turboprop aircraft have previously carried out Gagan-assisted approaches, the latest operation represents the first successful application on a commercial narrow-body jet.

A landmark moment for indigenous aviation technology

The achievement highlights years of work by the Indian Space Research Organisation (ISRO) and the Airports Authority of India (AAI), which jointly developed Gagan, short for GPS Aided GEO Augmented Navigation.

Unlike conventional landing systems installed at airports, Gagan enhances satellite navigation by improving the accuracy and reliability of GPS signals received by aircraft. The system operates through the GSAT-8 and GSAT-10 communication satellites, providing continuous coverage across Indian airspace.

The successful commercial deployment demonstrates the technology's readiness for wider operational use as India expands its aviation infrastructure.

Why ordinary GPS is not enough

Consumer GPS is sufficiently accurate for road navigation but does not meet the stringent safety requirements of commercial aviation.

Aircraft approaching a runway during poor visibility require highly precise horizontal and vertical guidance. GPS signals alone can become inaccurate while passing through the ionosphere, where atmospheric conditions may delay or distort the signals.

India faces an additional challenge because it lies beneath the equatorial ionisation anomaly, a region where ionospheric disturbances are more frequent and can produce larger positioning errors.

Gagan addresses this problem by continuously correcting GPS data and monitoring whether the signal remains reliable enough for flight operations.

How Gagan improves navigation

The correction process combines ground infrastructure with satellite technology.

The system operates through:

• 15 reference stations positioned across India with precisely known locations.
• Continuous comparison between the stations' actual positions and GPS-derived positions.
• A central processing facility that calculates corrections for any detected GPS errors.
• Transmission of correction data through GSAT-8 and GSAT-10 satellites.
• Automatic application of these corrections by the aircraft's onboard receiver.
• Continuous integrity monitoring that alerts pilots within seconds if navigation data no longer meets aviation safety standards.

This combination enables aircraft to receive highly accurate positioning information throughout their approach.

The significance of the Udaipur landing

During the approach, the IndiGo aircraft performed an LPV (Localiser Performance with Vertical Guidance) procedure.

LPV approaches provide pilots with both lateral and vertical guidance during landing and can deliver performance comparable to a conventional Instrument Landing System (ILS).

The key difference lies in the infrastructure.

Traditional ILS requires specialised ground-based radio equipment at every airport, along with regular calibration and maintenance. Installing and maintaining these systems across India's growing network of regional airports involves substantial investment.

Gagan offers a satellite-based alternative by delivering precision guidance without requiring the same level of airport-specific ground infrastructure.

Why regional aviation stands to benefit

The milestone comes as India continues expanding air connectivity to smaller cities under broader regional aviation initiatives.

Many regional airports still operate without advanced precision landing systems. Satellite-guided approaches could improve operational capability while reducing dependence on expensive ground installations.

Potential benefits include:

• Safer operations during poor weather and low visibility.
• Reduced flight diversions caused by weather conditions.
• Improved access to airports with limited navigation infrastructure.
• Lower infrastructure costs for expanding airport networks.
• More reliable schedules for airlines operating regional routes.

Industry observers have long viewed satellite-based augmentation systems as an important step towards improving accessibility across emerging aviation markets.

More than a navigation upgrade

Gagan is often confused with NavIC, India's independent satellite navigation system, but the two serve different functions.

NavIC determines an aircraft's location. Gagan does not replace GPS or NavIC. Instead, it verifies, corrects and continuously monitors satellite navigation signals, ensuring they meet the integrity and accuracy standards required for civil aviation.

According to ISRO, Gagan has two principal objectives:

• Providing the accuracy, reliability and integrity required for safe aircraft approaches.
• Supporting more efficient flight paths and better air traffic management across Indian airspace.

The system has also been designed to work alongside satellite-based augmentation systems operated by other countries, allowing compatible aircraft to transition seamlessly between different airspace regions.