It says “Download Error” repeatedly

Go into your iPad ‘Settings’ app and find Oz RWY in the list. If using a SIM card ensure that 'Mobile Data' is switched on. Also ensure you have data remaining on your mobile plan.
The other thing to check is that you’re not on public WiFi (and haven’t logged in yet), and check that you can reach ozrunways.com in Safari.

Also try killing the app from background:
https://support.apple.com/en-au/HT201330 (these instructions are for an iPhone but it works the same way on iPad.)