If you don't have a bag, you don't need to go landside.

@Calchas That's true enough. Though I think it's quite unlikely that the OP was traveling from India to Ecuador without hold luggage.

Actually, checking TIMATIC there doesn't appear to be a stipulation that the transit be airside.

@Calchas Transit is irrelevant from the airline's perspective, since the itinerary terminates in AMS. They are going to check whether he can enter the country. And they should have done so in Mumbai.

That is not my experience when doing visa-less transits across separate tickets when a visa would be required but for the transit. The airlines simply want to see onward flights. The wording is "onward tickets", not "onward flights on the same ticket".

@Calchas And what did you do about your checked luggage? There are a very few airports where you can claim your baggage airside (such as IST), but it's not common, and I don't believe AMS is one of them.

@MichealHampton I don't check luggage. In several recent instances I did a landside transit anyway. But as I only fly on oneworld carriers I would have got the bags through-checked onto the new ticket if necessary.

@MichaelHampton good, but source please. According to ec.europa.eu/dgs/home-affairs/e-library/documents/policies/… (via ec.europa.eu/dgs/home-affairs/what-we-do/policies/…), Indians are required to have an airport transit visa only in CZ, DE, ES, FR airports.

@Calchas depends on nationality and first airport though. «Traveling to a Schengen State via another Schengen State airport is not considered an airport transit neither is travelling to a non-Schengen country via two Schengen state airports. All flights between two or more Schengen States are considered to be «domestic» flights. Depending on your nationality, you might need a short stay visa as you enter the Schengen area – even if the stay only lasts a few hours ... » ec.europa.eu/dgs/home-affairs/what-we-do/policies/…

@Nemo An airport transit visa is for airside transit. The OP needed to transit landside, which requires a normal short stay type C Schengen visa.

@Nemo Turkey is not Schengen. Ecuador is not Schengen. Which two Schengen states are you referring to?

Usually TIMATIC distinguishes on the visa requirements between airside and landside transits. Here it simply says that a visa-less transit onto the next available flight is allowed. I do not blame the airline for not knowing what to do (well they should have called Dutch immigration to discuss).

@Calchas You still seem to be confused here. Again, a landside transit requires passing immigration and he still needs a Schengen visa. There is no reason for the airline to even be looking at the transit section at all.

@MichaelHampton I'm not confused, perhaps I have not been clear. Sometimes a landside transit, via the immigration desk, is allowed by the immigration authorities. If the transit allowance is limited to airside, this is usually stated very clearly in the TIMATIC feed. In this case, it merely says "transit" without qualification.

@MichaelHampton No need to shout. The airline can consider it a transit, even if one goes landside, even on separate tickets. As I say, I have done this before (in particular in China). I am happy to accept that this may be disallowed in this specific case, although it is a bit unfortunate that it is not made clear in TIMATIC.

Everyone is correct here to a degree. Airlines are required to check that a boarding passenger meets the entry rules for the destination of their ticket. The airline is not required to consider additional tickets in the passengers possession but conversely they are not prohibited from doing so. In this case it appears that Mumbai ground staff took his second ticket into consideration and Istanbul ground staff did not. Both calls were technically correct and proper, but understandably Istanbul's decision was frustrating.

@Doc I wasn't referring to any Schengen state, I was pointing out that Calchas' examples are useless if the involved airports/countries are not mentioned.

@Calchas It's a bit complicated to figure out as you need to read several parts of the regulations in conjunction but the Schengen Borders and Visa code are clear, all the exemptions for transit are for airside transit, Indian citizens need a visa for everything else. So TIMATIC seems indeed a bit misleading on this one, which might have contributed to the difficulties faced by the OP.

Given the updated information the original answer given here is incorrect. The updated answer is also incorrect, as the OP would have clearly provided details of his connecting flight. Your link to Timatic is also misleading as it is for the Netherlands as a destination, not a connection point.

@Doc You assume too much. The OP might not have provided any details of his second ticket to the staff in Istanbul. Or they might have misunderstood him or ignored him. As for the original answer, of course it's incorrect. That sort of thing happens when people radically alter their questions...

@MichaelHampton He "radically" alerted his question because I asked him for further information, rather than just answering based on guesses around things like luggage...