The train in the night from June 1 to June 2 ran up to 29 minutes late but then caught up and arrived in Gdansk on time (there's a lot of buffer in some places, with several 10 or even 20-minute stops during the night).
Last night's train only ran up to 10 minutes late, but again caught up before getting to Gdansk.
The free version of Zugfinder shows that the train is usually on time at the final destination, but that there can be delays en route (you have to subscribe to see the details of where it got delayed and where it caught up).
However I'm not sure of the reliability of the data for this train on Zugfinder: for the train departing on June 1st, it shows a maximum delay of 11 minutes (at Gdansk Wrzeszcz) while PKP says 29 minutes from Żmigród to Poznań Główny and on time at Gdańsk Wrzeszcz. Sadly the PKP website doesn't allow going back further in time (not that I could find, at least), and ČD does not give delays for earlier trains at all.
The likelihood that the train will be on time is therefore quite high, but you can't quite exclude delays.
However, even if it's on time, that seems to be relatively tight to me:
- Taking a taxi to the airport, you will probably get there around 5:20-5:30
- Your flight is at 7:10 and the gate closes 30 minutes before departure, so you need to be at the gate by 6:40 at the latest.
So that leaves you one hour to go from the curb to the gate + buffer for any delays.
If you have your boarding pass in hand and no checked luggage, and since you are departing to a Schengen country you can go directly from the curb to your gate with just security to go through.
In terms of distance, this does not seem to exceed 400 m, which should take about 5 minutes, so it's all about the security queue (and process).
I'm not familiar with Gdansk and how long the queues can be at security (I can't seem to find any info online), so I don't know how much buffer that leaves you with.
Note that in some airports, at some hours, when you arrive by car (including by taxi), the last few hundred meters to reach the terminal can be excruciatingly slow as the terminal approaches are jammed. No idea if that is the case in Gdansk nor if that would apply at 5:30am on a Sunday (hopefully not).
All in all, if there are no major delays, it's perfectly doable, and you probably have a bit of buffer (probably about 30 minutes), but not a lot.
I definitely wouldn't mind that timing if I could easily switch to another flight (flexible ticket, frequent flights on that route, no hard constraint on the time of arrival at my destination), but I would be a bit worried with that timing if missing that flight would really be a problem.
Also I'm not sure what is you experience with night trains, but personally I have a hard time sleeping on those. YMMV.
Edit 04/06/2025
Last night’s train arrived at Gdańsk Główny 26 minutes late, and at Gdańsk Wrzeszcz 34 minutes late.
Edit 05/06/2025
Last night's train ran a full 60 minutes late through Gdańsk.
I think we can now conclude that you can hardly rely on it running on time.
