Updated: January 22, 2022 8:19:57 pm
Flights to the United States from India resumed on Thursday as the Federal Aviation Administration (FAA) cleared the landing of more aircraft even in low-visibility conditions, despite the rollout of C-band 5G technology.
Following the announcement, Air India resumed flights from India to the US, with the first flight for John F Kennedy International Airport in New York departing in the morning.
Why had AI suspended its US flights?
On January 14, the FAA warned that the rollout of new 5G technology by AT&T and Verizon in the allotted 3.7-3.98 GHz (gigahertz) band could potentially lead to interference with onboard instruments such as radar altimeters.
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Commercial passenger and cargo airlines had also warned of an impending “catastrophic” aviation crisis if the rollout of 5G went ahead as planned.
Early on Wednesday, AI announced it would not be operating eight India-US flights — on the Delhi-New York, Delhi-Chicago, Delhi-San Francisco sectors — that day “due to deployment of the 5G communications in the US”.
Besides AI, US-based American Airlines and Delta Airlines operate direct flights between the countries. These carriers, too, cancelled their flights on Wednesday.
The deployment of 5G by AT&T and Verizon, two of the biggest wireless communications service providers in the US, has triggered concern among airlines, who have said that the frequencies used by the telecom companies is very close to the frequencies used by onboard instruments such as radar altimeters, which operate in the 4.2-4.4 GHz range.
How do flight radar altimeters help in safe flight operations?
For all airborne vehicles — an aircraft, spacecraft, or even a missile — an altimeter is crucial to gauge the altitude and the distance covered.
Altimeters are of three main kinds: barometric, laser, and radio or radar altimeters. Most commercial passenger and cargo aircraft use a combination of all these altimeters along with global positioning system (GPS) to determine their path, as well as factors such as height above sea level, presence of highrises, mountains, and other obstacles, and the likely flying time.
The radio or radar altimeter is a very small, low-power radar system that operates in the 4.2-4.4 GHz frequency microwave C-band. The high frequency of these altimeters enable aircraft makers to install small antennae that produce powerful signals that can be relayed quickly and accurately.
Why is there concern about radar altimeter interference specifically in the US?
Although the rollout of 5G by telecom service providers has been a cause of concern for aviation everywhere, the situation is critical in the US, which auctioned 5G bandwidth in 2021 in the 3.7-3.98 GHz on the C-band spectrum range. This band is very close to the 4.2-4.4 GHz range in which radio or radar altimeters operate, airline companies have complained.
According to industry experts, there are chances of interference of the two bands as telecom service operators, in order to extract the full value of 5G and give customers the best experience, push operations to the highest band possible. Altimeters too need to operate at higher frequencies in order to get the most accurate readings possible.
What is the situation in India?
In India, where 5G is yet to be rolled out, the frequency range for 5G telecoms operations is pegged around 3.3-3.68 GHz. It is learnt that the Federation of Indian Pilots has, in its meetings with the Department of Telecommunications (DoT), expressed concern about the frequencies being close together.
The DoT however, assured them that there would be no interference as the frequencies for commercial 5G services were at least 530 MHz away from those used by altimeters.
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