Scare in the skies, but ATCs are trained to handle such emergencies

There was panic at the Kolkata airport on Thursday morning as a BSNL link failure led to the air traffic control ( ATC) losing contact with as many as 300 aircraft for over an hour.

But the Kolkata ATC managed the situation by informing some pilots who then started coordinating with other pilots. Kolkata also sought help from Nagpur and Varanasi ATCs to track aircraft, and distances between planes were increased to prevent any untoward incident.

Despite the scare in the skies, the communication breakdown did not cause any major issues as ATCs are trained to handle such exigencies.

Here's a look at what exactly happened at Kolkata airport:

# All BSNL lines go down in Kolkata ATC office at 7.35 am

# VHF radios that work on VOIP went silent

# VHF frequencies 125.9, 132.35, 133.75, 125.775 went off air

# As BSNL carries data from radar stations and surveillance equipment, many radar screens went black

# Contact with majority of the 85 aircraft flying at that time was lost

# Connection with secondary surveillance radars in Jharsuguda (Odisha), Khatiar, Guwahati, Vizag and Behrampur was lost

# Kolkata airport, Badu in North 24 Parganas and Behrampur radars were functional

# Air space coverage was limited to only 200 nautical miles around Kolkata airport

# As all phone lines went down, ATCs used one mobile phone (available for emergency) to coordinate with nearby airports like Dhaka and Yangoon

# ATC officials then reached out to Varanasi and Nagpur ATC to relay instructions to aircraft

# Pilots within 200 nautical mile range were told to relay message to pilots flying beyond the coverage area

# Surprisingly, all aircraft landed on time and safely. No safety barrier was breached

# Despite being under pressure, 35 ATC officers on duty saved the day because of training to handle adverse situation

Shortly after the incident, the Directorate General of Civil Aviation (DGCA) stepped in and sought a detailed report on the incident while the Airport Authority of India (AAI) said there was no safety issue at all.

Union Civil Aviation Minister Ashok Gajapathi Raju too said the scare in Kolkata would not be tragic as there were alternate ways to communicate.

"It generates a scare. Lines can go down but we have alternative arrangements in India. Skies are monitored well," Raju said.