Probably you would need to wait for a month ( maybe longer ) to confirm which airport you're landing.
It's just Turkey, some of the authorities think that postponing an airport movement is similar to delaying an opening of a metro line.

postponed to April
 

I have good news and bad news about the airport,

First, I would start with the bad news;

Due to bad weather conditions and because the aircraft had shifted right while gaining speed, the captain of TK 2030, flight from ISL to Izmir, today had decided to close engines on the runway. I think that this issue is related to the winds that surrounded the area. Also, tonight ( 23 Feb ) TK flights to Adana, Baku and Tbilisi had been cancelled as a precaution.

However, the good news is that the IGA Lounge had opened to service and waiting it's customers. However, there is no official announcement that which lounge memberships would be valid or which airlines would contract this lounge. The only thing that I know is that TK would contract this lounge until their own lounges open to service.

I very much wonder, what happened to the passengers of those 4 cancelled TK flights. According to civil aviation (international) practice the airline (i.e. THY) is not obliged to provide any accomodation (even F & B) to those pax, except for any transfer passengers. But, I don't know what was done in practice, to provide customer satisfaction. The terminal itself has very little facilities (if at all!) to cater for those possibly 500 pax. The terminal hotel is not opened, the F & B outlets were possibly closed for the day and the seats in the terminal are indeed very very uncomfortable (made of hard ABS/plastic) to sleep on them.:(

EDIT: Indirectly, I heard that the passengers were bussed (by Havaist vehicles) to different locations in the City and some were given accomodation at the hotels (there may be some transfer pax).

Unfortunately, nothing official yet. The NOTAM still indicates that the IST code would move to Istanbul Airport on 2 March 2019 03:00 ( GMT +3 ). In addition, the TK website still indicates that the movement would take place on the 3rd of March. In addition the same link, has the statement "Following the finalization of relocation from Istanbul Ataturk Airport, the scheduled flights from Istanbul Ataturk Airport will end.". However, how they can still sell tickets from both IST and ISL codes then. Literally, this means that either the movement would not happen on the date announced or Atatürk and Istanbul Airport's would be used together. I am also relating this to the communications and public relations departments of Turkish Airlines as they are so weak and they are leading passengers to worry about their flights. TK is losing lots of customers as people don't want to be involved in the movement, as there is also a possibility that there could be small issues after the movement. I have wrote this same thing on one of the Turkish forums but it was deleted by the moderators, few minutes after I published this. In that text I have also criticized why Turkish Airlines is not anymore the best airline of Europe or why have decreased to the 18th in the Skytrax ratings. However, this part is not related to Istanbul Airport and does not directly relate to the subject. I would also like to mention that the issue here is not similar to Brandenburg Airport. In Brandenburg, there are issues with the terminal buildings which would not literally affect the airport operations if all flights operate from the Schönefeld Terminal but in this case, we have lot's of question marks which we don't know about ISL. For now, ISL is ready to be the 3rd airport of Istanbul but not the major airport of a city with a population of 20.000.000 nor the hub of Turkish Airlines.

I'm due to transfer through Istanbul that day, so if that's the 'official' day, the airports will be closed is my understanding. When will TK tell me this? I'll need to fly a different airline / route now....all very chaotic.

Anybody does not know the answer right now. If they follow a similar schedule like the past NOTAM and if your flight departs from IST until 03:00 on the 6th of April; you should probably be fine.

Thanks...but it arrives at 5:30 am or so on April 5, and then departs at 7:30 am from IST, right when I guess the airport would be closed (if this turns out to be the official date, of course).

Flights from Istanbul Airport ( ISL ) during the daytime on 5 April is open to sale. Probably as I mentioned before, your flights wouldn't have a problem unless they depart after 03:00 on 6 April. In your case, you would use Atatürk Airport for both of your flights.

For all other visitors to this thread, both airports are going to be open on the daytime of 5 April.

Ahhh, thanks. I thought the tickets from ISL to limited destinations were only on sale through April 4, with April 5 as the possible moving date. I appreciate all the useful information you post on this thread!

Well, the mystery is as follows:

1) On 5th of April, you can buy tickets from both IST (Atatürk AP) and ISL (New Istanbul AP). The flights from ISL are the limited number of "promotional" flights...
2) On 6th of April and onwards, TK System still sells tickets from IST (Atatürk AP) but you can fly nowhere from ISL. It's obvious that no TK ISL flights have been entered to the system (yet).

So to me, it's still a very gray situation, as what the status will be starting with April 7th (00:01 a.m.).

And the "official" notice which is the NOTAM issued and already in practice points out to the date of March 3rd (versus April 7th)!!!:mad:

Maybe the departed DHMI person took the password with her to change the NOTAM?!?!?

The new NOTAM is now released. The official movement dates are 5-6 April.

However that bookings are open for flights with the code ISL on 5 April. The NOTAM states that ISL 'Istanbul Airport' would be closed to air traffic on the 5th.
In addition, this time, instead of 3 days, they are planning to move within 2 days.

IST LaX