3 book series, post major nuclear event, North America, pilot crashes among a native people surviving overground.

[Blaise barron]

Key plot - based in North America , over ground North American style people survive with strange body markings, a pilot crashes among them, young man, taken captive , from the underground militaristic society post a major nuclear event that blighted the world. The plot revolves around the relationship between the pilot, a girl and a boy from the tribe and how the two societies are at war with each other.
About 3 books in the series.
From the 90s, the contrast between the high tech over crowded underground and the open skies more native society..

Thanks!!!

 

[The Judge]

The Amtrak Wars series by Patrick Tilley?

 

[monkeypooper]

The Amtrak Wars series by Patrick Tilley?

Definitely I'd say but more than 3

 

[monkeypooper]

1. Cloud Warrior (1983)
2. The First Family (1985)
3. Iron Master (1987)
4. Blood River (1988)
5. Death Bringer (1989)
6. Earth-Thunder (1990)

 

[Luiglin]

Great series, with some really interesting ideas.

Edited: for spoilers

 

[Danny McG]

The one element that really sticks in my head was the Kojak braves, so called because they all shave their heads - what a trivial detail to always remember!

 

[monkeypooper]

I've got to say I also had the illustrated guide and it's not needed when reading but quite an addition