For around two minutes on April 5, dozens of passenger aircraft flew blind over Mumbai, as a workstation of the air traffic system that coordinates flights crashed twice. Air traffic controllers said the system, one of four machines part of the guiding system called Lower Area Control (LAC), crashed because the Mumbai airport is managing a 60% rise in air traffic following Pakistan’s closure of its airspace in February. Pakistan shut its airspace after India’s retaliation to the Pulwama attack, and has not fully opened it. Hundreds of more flights from the east are flying over Mumbai every day.

If a systems crash is not alarming enough, consider this. The Mumbai air traffic control (ATC) is using a decade-old system with no backup if it fails to restart. For four months, the system has been running without maintenance, as the contract with the firm that developed it ended in December 2018. Airports Authority of India is yet to appoint a new maintenance contract. When systems were down on April 5, the ATC simply waited for it to restart. If that didn’t happen in 10 minutes, ATC would have switched to the manual Procedural Control system, less efficient as it does not display floght movements. Controllers said they faced a crash for the first time on March 30, and were worried about the overloaded system crashing again.

“Once the system crashes, we are not sure if we can handle the traffic manually. It could lead to a total shutdown of the Mumbai airspace,” said an AAI official, not wishing to be named. On Saturday, a day after the crash, the Air Traffic Controllers Guild (western region), wrote to their general secretary in Delhi. HT has a copy of the letter, which points out that the maintenance contract ended in December and that the system in its current form is a threat to aircraft safety.

The AAI spokesperson, however, sought to downplay the issue. “In any software system, glitches are always there,” said the spokesperson JB Singh, in a statement. “The display at a particular sector in Mumbai froze and had to be restarted. It became normal in 20 minutes, and during this period, the sector’s airspace was combined with the adjoining ATC sector (Ahmedabad or Nagpur), ensuring safe delivery of service.” Singh, however, confirmed that the Mumbai automation system was due for replacement. “Tendering action is in progress for a complete replacement. These system glitches are common and happen worldwide,” he said.

Other senior AAI officials said the issue with the system has already been discussed at the senior-most levels in Mumbai and a proposal to have a new system was sent to AAI’s headquarters in Delhi. But, it will take at least a year to finally replace the system, after tenders are issued and the bidding process starts, these officials said.

For now, to reduce its traffic load, the Mumbai airport has issued a notice to pilots and airlines that use its airspace to not request a direct route over Mumbai, and instead follow their regular route. “This notice to airmen (NOTAM) may last up to a month and is essential. Without it, the load on controllers increases,” airport officials said.

Usually, 55 ATCs work each shift. But, now, 66 of them have been posted for the night-time peak hour to cope with additional traffic. Another measure taken by the ATC is setting up a radar and remote voice communication system at Porbandar.

First Published: Apr 09, 2019 02:05 IST