Do Admins run tester airlines on new worlds?

Because the last few worlds ive noticed airlines with the same names doing really well then they tend to quit after about 2 months.

In the new long term world, there is an airline with 75 planes in less than 4 weeks, without used aircraft and another with 62, the next highest is about 40 at time of reading, most airlines are around 20.

No. Team members can play on public game worlds (and might often use repetitive names), but we’re not generally opening airlines to test every new game world.
What you’re seeing with large airlines liquidating, might either be some players enjoying to always switch to the latest game world - or at least some of those aren’t leaving by their own choice…