Units

Units cannot be retrofitted - you'll have to scrap or jettison them, then rebuild.

The easiest way to get rid of 500 fighters would probably be to load them into a transport, and then fire on that transport - you don't want to have to scrap 500 fighters one by one...

Or just send them into combat, and do some damage in their "scrapping mission."

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No, youd don't get your money back for your units. You can't use the scrap command on your loaded transport over a planet. The transport will drop its units onto the planet and then be scrapped. Leaving you with your units still. Use the FIRE ON command and your ships will blow up your transport and all the units inside.

Or you can launh the fighters, and scrap the fighter group...

No cargoship needed.

Sadly, you can't do that for troops and weapon platforms.

You can use ctrl+K to scrap cargo on the planet.

Did you ever try to scrap 300 troops using ctrl+K?

Nope. But I've never felt the need to scrap troops. I usually just use my old troops as cannon fodder.

That, to me, seems like a feature that needs some updating then.

Oh and if you're playing stock fighters do just pwn everything