Ever found your mobile phone's signal to be patchy while waiting for a flight? That’s because telecom operators can’t provide stronger signals near airports, as these can interfere with a small cockpit tool—a radio altimeter.

The electronic gauge, which measures the altitude of an airborne plane, feeds data to multiple automated systems on board. A wrong reading can be a safety risk, especially during poor visibility. But the restrictions have sparked concerns as telecom operators expand 5G coverage and prepare for even stronger 6G networks.

Now, the civil aviation regulator has asked all airlines to modify the altimeters so that they are tolerant to 3,300-3,670MHz C-band—a key range of spectrum to provide 5G services, according to the Director General of Civil Aviation (DGCA) order dated 19 November 2025. Mint has reviewed a copy of the order.

The required modification or retrofitting must be completed by 31 December 2027, the order said.

India is not alone in facing this challenge. Countries such as the US and those in Europe have faced similar challenges, with regulators proposing deadlines extending to 2029–2032 for full fleet retrofits. But that has also caused a spike in demand. According to estimates by the American regulator Federal Aviation Administration (FAA), upgrades will cost around $4.5 billion for the US fleet alone.

To be sure, the US had earlier addressed 5G interference concerns by requiring upgrades to aircraft radio altimeters, setting a February 2024 deadline. It later said the entire airline fleet had completed these upgrades by September 2023, mitigating immediate risks. However, the country now has plans to expand 5G into a higher spectrum band.

Since the 2022 rollout of 5G in India, telecom operators have had to limit signal strength near airports and follow strict exclusion zones to avoid interference with aircraft systems. According to the November order, the DGCA has also prohibited pilots from conducting automatic landings and from using enhanced flight vision systems for touchdown in aircraft with radio altimeters that are not tolerant of 5G airwaves.

“There are airplanes with an old generation of altimeters, which can cause interference with 5G currently and 6G in the upper C-band in future such as 4.4-4.8GHz,” said Bharat Bhatia, president of ITU-APT Foundation of India, which works with industry and government on telecom policy. “The altimeter replacement is the only solution, which could take time owing to a similar demand from other developing countries.”

According to Bhatia, current rules restrict 5G operations within 2.1 km of the runway ends and within 910 metres of the runway centreline—zones that cover terminal areas at most Indian airports. It effectively limits 5G deployment within airport premises, he said.

The extended band, such as 3.7-4.2GHz, which is allowed to support 5G services in other countries, is restricted in India, he said.

In response to Mint's emailed queries, Boeing said, “We’ll defer to the airline operators for any comments". Honeywell Aerospace, a key manufacturer of radio altimeters used in planes, said, “We are currently in direct engagement with the concerned authorities, including civil aviation ministry and DGCA and are responding to the query.”

Queries emailed to the department of telecommunications (DoT), the civil aviation ministry, IndiGo, Akasa, Spicejet, the Cellular Operators Association of India (COAI) on the matter did not elicit any response until press time.

“Regarding the 5G rollout, as part of a wider industry coalition, we continue to work with the FAA and other involved agencies to study the issue further and work toward solutions,” Airbus said in a statement.

An Air India official said that work on retrofit or upgrade of altimeters started “long time back”. “The airline will be fully compliant before the said deadline,” the official said. “Some of the narrow-body Airbus aircraft we have are already updated and work is ongoing in some,” the official said, without giving a breakup.

Operators rely on in-building networks

To be sure, telecom operators are also relying on in-building solutions inside airports and 4G spectrum bands such as 2,100MHz and 2,300MHz for mobile services.

There are concerns regarding 5G/6G services, but 6G is expected only by 2030, said a government official, speaking on the condition of anonymity. “The expectation is that the altimeters can be modified before that.”

There is a global demand for replacing such altimeters, which is delaying the replacement process in India, said an executive with an aircraft maker. Airline operators have been working with aircraft and equipment manufacturers to fix altimeters for the past couple of years, the executive said.

According to FlightGlobal, a London-based aerospace publisher, airlines in the US say they can speed up altimeter upgrades for 5G but want compensation for the costs involved.

Ever found your mobile phone's signal to be patchy while waiting for a flight? That’s because telecom operators can’t provide stronger signals near airports, as these can interfere with a small cockpit tool—a radio altimeter.

The electronic gauge, which measures the altitude of an airborne plane, feeds data to multiple automated systems on board. A wrong reading can be a safety risk, especially during poor visibility. But the restrictions have sparked concerns as telecom operators expand 5G coverage and prepare for even stronger 6G networks.

Now, the civil aviation regulator has asked all airlines to modify the altimeters so that they are tolerant to 3,300-3,670MHz C-band—a key range of spectrum to provide 5G services, according to the Director General of Civil Aviation (DGCA) order dated 19 November 2025. Mint has reviewed a copy of the order.

The required modification or retrofitting must be completed by 31 December 2027, the order said.

India is not alone in facing this challenge. Countries such as the US and those in Europe have faced similar challenges, with regulators proposing deadlines extending to 2029–2032 for full fleet retrofits. But that has also caused a spike in demand. According to estimates by the American regulator Federal Aviation Administration (FAA), upgrades will cost around $4.5 billion for the US fleet alone.

To be sure, the US had earlier addressed 5G interference concerns by requiring upgrades to aircraft radio altimeters, setting a February 2024 deadline. It later said the entire airline fleet had completed these upgrades by September 2023, mitigating immediate risks. However, the country now has plans to expand 5G into a higher spectrum band.

Since the 2022 rollout of 5G in India, telecom operators have had to limit signal strength near airports and follow strict exclusion zones to avoid interference with aircraft systems. According to the November order, the DGCA has also prohibited pilots from conducting automatic landings and from using enhanced flight vision systems for touchdown in aircraft with radio altimeters that are not tolerant of 5G airwaves.

“There are airplanes with an old generation of altimeters, which can cause interference with 5G currently and 6G in the upper C-band in future such as 4.4-4.8GHz,” said Bharat Bhatia, president of ITU-APT Foundation of India, which works with industry and government on telecom policy. “The altimeter replacement is the only solution, which could take time owing to a similar demand from other developing countries.”

According to Bhatia, current rules restrict 5G operations within 2.1 km of the runway ends and within 910 metres of the runway centreline—zones that cover terminal areas at most Indian airports. It effectively limits 5G deployment within airport premises, he said.

The extended band, such as 3.7-4.2GHz, which is allowed to support 5G services in other countries, is restricted in India, he said.

In response to Mint's emailed queries, Boeing said, “We’ll defer to the airline operators for any comments". Honeywell Aerospace, a key manufacturer of radio altimeters used in planes, said, “We are currently in direct engagement with the concerned authorities, including civil aviation ministry and DGCA and are responding to the query.”

Queries emailed to the department of telecommunications (DoT), the civil aviation ministry, IndiGo, Akasa, Spicejet, the Cellular Operators Association of India (COAI) on the matter did not elicit any response until press time.

“Regarding the 5G rollout, as part of a wider industry coalition, we continue to work with the FAA and other involved agencies to study the issue further and work toward solutions,” Airbus said in a statement.

An Air India official said that work on retrofit or upgrade of altimeters started “long time back”. “The airline will be fully compliant before the said deadline,” the official said. “Some of the narrow-body Airbus aircraft we have are already updated and work is ongoing in some,” the official said, without giving a breakup.

Operators rely on in-building networks

To be sure, telecom operators are also relying on in-building solutions inside airports and 4G spectrum bands such as 2,100MHz and 2,300MHz for mobile services.

There are concerns regarding 5G/6G services, but 6G is expected only by 2030, said a government official, speaking on the condition of anonymity. “The expectation is that the altimeters can be modified before that.”

There is a global demand for replacing such altimeters, which is delaying the replacement process in India, said an executive with an aircraft maker. Airline operators have been working with aircraft and equipment manufacturers to fix altimeters for the past couple of years, the executive said.

According to FlightGlobal, a London-based aerospace publisher, airlines in the US say they can speed up altimeter upgrades for 5G but want compensation for the costs involved.