Fine, but it's retconning within the season. With that tech, there'd be no reason for them to look the way they do, which is a good orbit/lunar vessel ill-suited to atmosphere - a great design for their designed purpose pre-breakaway which can't fulfil its ongoing series role without magic tech.The Eagles do have anti-gravity shield & screen technology as stated in episodes and listed under propulsion in this link:
http://catacombs.space1999.net/main/cguide/umeagle.html
Frustrating thing is that it wouldn't be so magic if, for instance, we'd been told that Bergman's experimental forcefield from Black Sun would now be fitted to the Eagles, expanding their capabilities. As it is, we can I suppose fill in the gaps.