How airlines are staying punctual despite flight delays - Hindustan Times
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How airlines are staying punctual despite flight delays

May 15, 2024 04:19 PM IST

The menace of buffered block times has not gone away. That means on-time performance (OTP) of airlines is intact despite rising passenger complaints

Two flights are scheduled to fly from Delhi to Mumbai at the same time, but one is to reach in 115 minutes, while the other will take 135 minutes.

Delhi - Mumbai - Delhi, the busiest sector in the country sees block times which range from an hour and 55 minutes to two hours and 50 minutes for the non-stop flights(REUTERS)
Delhi - Mumbai - Delhi, the busiest sector in the country sees block times which range from an hour and 55 minutes to two hours and 50 minutes for the non-stop flights(REUTERS)

A little while later, the story is repeated with one airline taking 110 minutes, while the other takes 130 minutes. The plane types are either the same or similar. In fact, in one case, two airlines depart at the same time but one is scheduled to reach Mumbai in 130 minutes while the other one is to take 170 minutes and yes the flight is non-stop!

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The story of block times mismatch is one which refuses to improve year after year for the last many years and has a direct impact on On-Time Performance and thus passenger experience.

Data provided by Cirium - an aviation analytics company, exclusively for this article throws some interesting light providing insights which show the large variation in block times on the same sectors with similar or same aircraft. 

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There has been a lot of debate on the definition of block times, if it is calculated from doors closed to doors open or when the aircraft is on its own power or if it is from chocks-off to chocks-on. The variation in some cases is so large that no matter if airlines calculate it differently, it would still not make sense.

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The top sectors

Delhi - Mumbai - Delhi, the busiest sector in the country sees block times which range from an hour and 55 minutes to two hours and 50 minutes for non-stop flights. Airline-wise averages differ as well.

IndiGo averages 127 minutes (2:07) on Delhi - Mumbai, while Air India averages 140 minutes (2:20). The longest flight on the route by block time is with Air India at two hours and fifty minutes. Vistara’s average block time is 133 minutes. The difference in block time ranges from 115 minutes to 170 minutes. For the return sector, the spread is 120 minutes to 150 minutes. IndiGo averages 129 minutes while that of Air India is 138 and Vistara is at 132 minutes.

On the second busiest route in the country, Delhi - Bengaluru - Delhi, the average block time is 168 minutes (two hours and 48 minutes) with the shortest block time being 150 minutes by a Vistara flight, while the longest being 185 minutes - operated by SpiceJet. IndiGo’s average block time is 165 minutes, while that of Air India is 173 minutes and that of Vistara being 160 minutes. The return sector averages 170 minutes, with IndiGo, Air India and Vistara averaging 172 minutes, 174 minutes and 160 minutes respectively.

On the third busiest route in the country, the Mumbai - Bengaluru route, the average block time is 109 minutes (one hour and 49 minutes). IndiGo averages 106 minutes while Air India and Vistara averages 111 minutes. Akasa Air has a significant presence on the route and averages 110 minutes. 

While the average looks in line for everyone, the smallest block time is just 95 minutes or one hour and thirty five minutes on an IndiGo flight, while the longest scheduled block time is Two hours and five minutes (125 minutes) on Vistara and AIX Connect flights.

The story is the same across multiple other sectors. On the Delhi - Guwahati sector, the difference between the shortest published flight and the longest is 35 minutes, likewise for Mumbai – Chennai. For Delhi - Hyderabad, Mumbai - Lucknow the difference is 30 minutes while for Delhi - Pune, Mumbai - Kolkata it is 25 minutes, for Delhi - Chennai and Delhi - Kolkata it is 20 minutes.

Even for short sectors, like Delhi - Lucknow, the shortest and highest block time has a difference of 20 minutes while that between Bengaluru and Hyderabad is 25 minutes.

Building in the buffers?

Many years ago, IndiGo was accused of maintaining a high On Time Performance by having higher block times and building buffers and then reaching early. This practice is now being used by multiple carriers and has backfired for IndiGo as its OTP has seen a drop in recent months.

But why does this happen ? More often than not, at congested airports like Mumbai and Delhi, the airlines are forced to opt for slots that are on offer rather than the ones that are as per requirements. While sometimes the difference is 05–10 minutes, the difference could be as high as 20 or 30 minutes.

ALSO READ: Woman recounts airport ordeal amid IndiGo flight delay: ‘Diabetic patients made to eat sugary food’

The only way to adjust the block time then is to change the departure timings at the origin, which if it is a congested airport may not be possible. India is uniquely characterised by airports that are under the control of the armed forces and civil airports, which have restrictions. Both these types lead to a shortage of bays or restriction on operating hours, eventually not allowing the airlines to change the timings at both or either ends and live with the timings which they have been offered.

While a flight has an inflated or short block time as the case may be, the flight ends up taking as much time as needed to traverse the distance. A flight that has inflated block time reaches early at the destination and the one that is short on block time ends up with a delay.

What does this lead to? One of the prime reasons for congestion and cascading delays is either an excessively short block time or a very long block time. In either cases it leads to air congestion and cascading effects at airports. A flight that comes very early, eats into the airspace planned for other planes and leads to delays. A flight that has a short block time will end up coming in late, thus intruding into the planned arrivals and departures leading to delays.

The solution is for airports and airlines to look for best possible swapping of slots to ensure that such flights are far and few, as is the norm globally. Will it happen? A lot depends on the will of just about the entire ecosystem.

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