Flight Plan

How flights get their numbers is no flight of fancy

Ashwini Phadnis | Updated on December 10, 2019 Published on December 10, 2019

Ashwini Phadnis offers a peek into a fascinating exercise — airlines assigning a unique identity to each of their flights

Have you ever wondered how the scheduled airlines in the country, which operate thousands of flights every day, decide their flight numbers?

A ‘flight number’ is a colloquial term which tells you which aircraft of which airline to board. The official term used for the numbers that airlines give their flights is ‘flight designator’ and is defined in the Standard Schedules Information Manual (SSIM) published annually by the International Air Transport Association’s (IATA) Schedules Information Standards Committee (SISC).

Typically, airlines and flight numbers are identified by two letters of the alphabet and the ‘flight number’ which refers to the numeric part (up to four digits) of a flight code. For example, in the flight codes BA2490 and BA2491, ‘2490’ and ‘2491’ are flight numbers while BA stands for British Airways. While the identifying letters of the alphabet for an airline are given by IATA, the flight numbers are decided by individual airlines.

There is near unanimity in the Indian aviation industry that there is no universal standard or code for deciding flight numbers. Airlines’ officials point out that this is because airlines have different scales, different fleet types and different ways of operating.

Giving the flights individual numbers is a complicated exercise and every airline follows some kind of rationale when deciding these numbers. For example, the youngest Indian airline flying in both domestic and international skies, Vistara, has chosen 6 to 9 as the first of the four digits that it uses for its flight numbers from the four different regions of the country, Vinod Kannan, Chief Strategy Officer of the airline, told BusinessLine.

So, it uses 6 as the first digit for flights to and from North India, 7 for flights from and to the East while 8 is for flights to and from South India. So its Hyderabad-Chandigarh flight bears the number UK 0830. The other numbers of the flight are also decided by the airline.

A senior retired official of Indian Airlines, which has now merged with Air India and operates under the name Air India, says that Indian Airlines had four bases, each base used a distinct first digit. For example, 1 was the code for Mumbai while 5 was for Chennai.

The complexity in giving numbers to flights does not end here. Says Kannan, “We have a hub in Delhi, so all flights going out of Delhi end with an odd number while all flights coming back to Delhi end in an even number.”

Another noteworthy thing about flight numbering is that the outbound flight is generally one digit less than the return flight. So SpiceJet’s early morning connection between Delhi and Bengaluru is numbered SG 191 while the return flight has the number SG 192 and Air India’s first daily flight between Delhi and Chennai is numbered AI 439 while the return flight is AI 440.

To make it easier for its flyers, Vistara also tries to ensure that when it operates multiple flights in a day to the same city, the earlier flight has a lower number while that departing in the evening has a higher number. “This gives the passenger some indication of what the timing of his flight is,” Kannan says. So, the first of its daily flights between Bengaluru and Mumbai, which leaves at 9.30 a.m., is numbered UK 0852 while the last of the daily flights linking the two cities is numbered UK 0866 leaving Bengaluru at 21.30 p.m.

Complicated though all this sounds, this is the simpler part of deciding on flight numbers. With the Indian aviation market growing and more flights being added, airlines do encounter problems in deciding on their flight numbers, especially when two flights are being operated by different airlines around the same time on the same ATC frequency.

An official whose airline faced such a problem explains, “The regulator asks us to avoid and in fact does not allow us to use the same flight numbers for flights departing at nearly the same time as there is conflict of call signs up in the air which can lead to some miscommunication. To be crystal clear two of the three digits used by two airlines should not match within a certain time frame. An airline which is already operating has precedence. Typically, because of historicity or respect the new airline tries to change its flight number and looks at the next available number or whatever else makes sense.” Earlier, flight codes had three digits and a flight with four digits meant that it was a code share flight. However, with airlines’ operations growing there is little option but to give their flights four-digit codes, airline officials point out.

Some iconic flights

Globally some airlines are also known to give unique numbers to their iconic flights. Says Ankur Bhatia, Managing Director, Amadeus Indian Subcontinent, “Pan Am (the now defunct Pan American Airlines) operated Pan Am 001 and Pan Am 002. These two flights circumnavigated the world, one going Eastwards and the other Westwards, and have traditionally been remembered only as flight numbers. Similarly, Air India’s non-stop service between India and New York is remembered as AI 101.”

Further, airlines do not like talking about it but if there is an incident or accident on a flight, it is not uncommon to retire that flight number. Air India operated flight IC 814 between Kathmandu and Delhi. The airline’s website now shows the flight being renumbered as AI 214. IC 814 was hijacked in 1999.

Published on December 10, 2019
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