They stick onto existing groups when you launch them.
You may have had a stack of 3 sitting around after battle losses killed them down to an odd number, and then tried to launch 8.
Those new ones stick onto the first fighter stack they see.
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If you load fighters up and relaunch, they'll all end up in the same stack.
You'll have to launch, move, launch, move...
They can only stick to existing stacks in the same sector, after all
