Is it collusion for companies in different industries to agree not to compete with each other?

For instance, if completely different companies like Coca-Cola, Microsoft and Ford agreed never to compete with one another by not entering into each others markets (Coke agrees never to make computers, Microsoft agrees never to make cars, etc.), is that a form of collusion?

Furthermore, would such an agreement be a violation of antitrust laws?

My understanding is that no, it isn't, to both. As long as both companies are not trying to artificially inflate prices in the market, it is completely acceptable business strategy. Of course, it's a completely different matter if it's ethical or not.

Not collusion

Yes.