I don’t think the dongles survive the heat any better than the RPi.
Also i was recommending a fan like this, cools both the dongle and the RPi.
You can clearly see when the fan was installed, temperature of the RPi dropped by 20 C
With the fan i’d say the RPi never goes more than 10 C above ambient.
So even if your attic gets to 60C, with a fan that should work.
Anyway installing it there is of course quite the chore if it’s that hot.
And having the RPi somewhat accessible is nice.
The problem seems to be that the reception isn’t even any better below the roof.
What happens if you connect the FA antenna with the SMA adapter directly to the FlightAware ProStick.
You obviously have some USB cable to connect it.
I’d just suspend the antenna from the ceiling wherever your RPi is.
Do you mean you moved them up only Tuesday and then moved them back down?
Running the rtl-sdr LNA would sure work in the attic.
You could get relatively inexpensive cable from the attic to the RPi and attach the LNA directly to the FA antenna.
To make sure the rtl-sdr LNA doesn’t get too hot, i’d get a bias-t and feed it with the 3.3 V rail from the RPi.
Or use 5V and a 20 Ohm resistor.
(Feeding it with 5V direclty will make it run rather hot)