(This story originally appeared in on Mar 17, 2017)

NEW DELHI: The boom in aviation in India has given rise to a peculiar problem — airlines are running out of flight numbers. With a growing number of flights and too few flight numbers, call sign confusion emerged as a serious concern among authorities at the recently concluded meeting for deciding summer slots.The existing three-digit codes are increasingly leading to confusion and there has been a spate of safety scares when similar sounding flight numbers operate to or from the same airport around the same time — something that’s happening with increasing frequency due to the volume of traffic.At the meeting, S B Sharma, Airport Authority of India ’s joint GM (air traffic management), said 1,800 call sign conflicts were resolved in the last season (last summer).According to the minutes of the meeting, Sharma requested airlines to follow guidelines for enhancing safety of aircraft.Lalit Gupta, joint DG and head of safety, Directorate General of Civil Aviation , too flagged the issue. “Even after detailed deliberations on call sign conflicts during last season, airline operators are filing new flights in the same route within a 15-minute gap, with similar call signs. They were advised to take cognizance of guidelines on the call sign conflict issue,” Gupta was quoted in the minutes as saying.Aviation authorities have for long been planning to end the confusion caused by similar sounding call signs or flight numbers by switching over from three-digit to four-digit flight numbers. But there has been no decision so far despite growing traffic.Till that happens, the regulator had taken some interim decisions like not allowing similar sounding call signs or signs with same digits in their numeric part to be flying within a space of up to two hours in the same region.All big Indian airlines use three-digit flight numbers that are suffixed to the airline code, such as AI for Air India . A few small airlines with a handful of daily flights have used four-digit numbers.