IndiGo's cut routes come back on Thursday. Saigon is not one of them.

IndiGo's summer suspensions expire on 30 September. Five of the six routes restart the next morning. The sixth, Kolkata to Ho Chi Minh City, does not appear in the airline's winter plan at all.

That is the sentence to hold on to if you are pricing Southeast Asia for Diwali or the weeks after it. Seats that disappeared on 1 July come back on Thursday. A Bangkok fare that looked punitive in August should look different by the weekend. Saigon is the exception, and it is a real one.

What was actually pulled

IndiGo announced six suspensions running from 1 July to 30 September, with Siem Reap starting two days later on 3 July. The destinations were Langkawi, Krabi, Ho Chi Minh City, Hong Kong, Shanghai and Siem Reap. The airline said it was aligning capacity with current travel demand while maintaining operational efficiency, and pointed at elevated operating costs and continued international airspace restrictions.

The six cancellations were the headline. They were not the whole of it. AeroRoutes, which reads airline schedule filings, published the full third-quarter picture on 3 June, and it is a longer list than anything the press releases carried:

• Delhi to Phuket cut from two daily flights to one.
• Mumbai to Bangkok Suvarnabhumi cut from three daily to two.
• Hyderabad to Bangkok cut from seven weekly to four.
• Bengaluru to Phuket cut from seven weekly to four. Kolkata to Phuket from six to three.
• Hyderabad to Singapore cut from seven weekly to three. Kolkata to Singapore dropped entirely. Tiruchirappalli to Singapore from eleven weekly to seven.
• Chennai to Penang cut from four weekly to three.
• Delhi to Denpasar, which routes through Bhubaneswar, dropped for the quarter.

Add those up and the summer was not six missing dots on a map. It was most of the India to Southeast Asia network running thin at the same time, on the same routes Indian families actually fly. Anyone who priced a Phuket trip in August and walked away because the fare made no sense now knows why.

What comes back, and what does not

The resumption date in those same filings is 1 October. Reporting from 9 September confirmed that Langkawi, Krabi, Hong Kong, Shanghai and Siem Reap all return then, with the caveat that it remains subject to market conditions. Ho Chi Minh City does not return to IndiGo's network plan. The Manchester route, which was a separate decision, ended on 31 August and is gone.

Air India is moving the other way on Vietnam. The same reporting has it restoring Delhi to Ho Chi Minh City, along with Delhi and Mumbai to Bangkok, Delhi to Kuala Lumpur, and Delhi and Mumbai to Singapore. So Saigon is not unreachable. It is a Delhi problem now rather than a Kolkata one, and if you are flying from the east that is a connection, a longer day and a different price.

The Thai carriers are adding while IndiGo restores

Thailand's low-cost airlines are doing the more interesting thing this winter, which is growing into India rather than waiting for Indian carriers to come back.

Thai VietJet is putting a bigger aircraft on Mumbai. AeroRoutes reported on Monday that the daily Bangkok Suvarnabhumi to Mumbai flight switches from an A320 to a Boeing 737 MAX 8 on 1 October, and that Phuket to Mumbai returns on 25 October at four flights a week. The Phuket timings are brutal and cheap in the way these things usually are: out of Phuket at 21:15, into Mumbai at 00:30 the next day, back out of Mumbai at 01:30 and on the ground in Phuket at 07:30.

Thai AirAsia is restarting a long list out of Don Mueang, and the India routes on it are not the obvious ones. Gaya comes back on 25 October. Ahmedabad on 6 November. Guwahati, Hyderabad and Lucknow on 16 November. Jaipur on 17 November. Don Mueang to Kuala Lumpur and Phuket to Siem Reap both restart on 25 October.

Look at that list again. Gaya, Guwahati, Lucknow, Jaipur. The Thai carriers are betting on second-city India while the Indian carriers consolidate around the metros. If you live in one of those cities, your winter just got easier in a way that has nothing to do with IndiGo.

Kochi is the one to watch

Cochin International Airport published its winter schedule on Wednesday, and it is the clearest single snapshot of where the season is going. The schedule runs from 26 October to 28 March. It carries 1,766 weekly flight movements across 32 destinations, 19 of them international, flown by 28 airlines. That is 14.4 per cent more than the summer schedule it replaces.

The new international route is Air India Express to Bangkok Suvarnabhumi, four times a week, which gives Kochi both of Bangkok's airports. Akasa Air goes daily to Dubai, Dammam and Kuwait. IndiGo goes daily to Fujairah. Managing director S Suhas put IndiGo at 638 weekly movements, the largest share at the airport by some distance.

A 14.4 per cent jump in one airport's weekly capacity is not a rounding error. It is the shape of the recovery, and it is happening in Kerala first.

What this does to your money

Capacity and fares move in opposite directions, with a lag. Through July, August and September you were bidding for a smaller pool of seats on the exact routes everyone wanted. From 1 October that pool widens again. Fares should follow, but not instantly and not evenly.

Three practical consequences.

• If you have been sitting on a Bangkok or Phuket booking, wait until next week before you buy. The seats being added are on your route.
• Diwali is Sunday 8 November. The returning routes are back well before it, but so is everyone else's demand. The cheap fortnight is late October, between the schedule change and the festival rush.
• If your trip runs through Kolkata to Vietnam, stop waiting. That flight is not coming back this winter, and the alternative goes through Delhi.

There is a Bali footnote worth knowing if you are planning further out. AeroRoutes reported in August that IndiGo's Delhi to Denpasar service keeps running through Bhubaneswar on an A320neo until 30 December, then switches to a nonstop A321XLR from 1 January. Mumbai to Denpasar still makes a stop at Chennai. The A321XLR that was meant to fix the Mumbai routing on 1 January has been pushed to 28 March at the earliest. A nonstop Mumbai to Bali is therefore not a thing you can book for this winter, whatever a booking engine suggests when it quotes you a single flight number.

What to do about it

• Recheck any Southeast Asia fare you abandoned between July and September. The reason it was expensive expires on 30 September.
• Book the last week of October if you can move. It sits after the schedule change and before Diwali pricing.
• From Gaya, Guwahati, Lucknow, Jaipur or Ahmedabad, price the Thai AirAsia flights out of Don Mueang directly rather than assuming you must connect through a metro.
• Check the flight number on anything that looks like a nonstop to Bali or Phuket. Several of these services carry one number and make a stop.
• Do not book a Kolkata to Ho Chi Minh City itinerary on the assumption the route returns. It is not in the plan.

What is still unclear

The 1 October restarts were described as subject to market conditions, which is an airline reserving the right to change its mind. The costs that caused the cuts, fuel and airspace restrictions, have not obviously gone away. Five routes returning is a schedule, not a promise.

Nobody has said whether Kolkata to Ho Chi Minh City comes back later in the winter, gets handed to another carrier, or simply ends. Silence on a route usually means the decision has not been taken rather than that it has.

And the A321XLR dates have already slipped once. A plan that moved from January to late March can move again, so anyone building a trip around a promised nonstop should keep a connecting option in reserve.

The cheapest week of this winter is probably the one between 25 October and 1 November. The seats are back and the festival demand has not arrived yet.

Everything above comes from schedule filings and airport announcements made in the last three weeks. Filings are the airlines' current intention, not a contract. Check the carrier's own page in the week you fly, because a route change reaches that page before it reaches anywhere else.