The landing strip theory always makes me laugh a bit because if ancient aliens needed a flat bit of Peru to park up, they've done a worse job than me reversing into a bay at Tesco. The lines only really make sense as ceremonial or astronomical markers when you dig into it, and Maria Reiche spent decades on that angle with pretty solid reasoning behind her.
That said I don't think the theory is fully dead, it just gets kept alive by people who haven't looked past the Von Daniken stuff. Worth noting the geoglyphs are visible from surrounding hills too, not just from the air, which kind of undermines the whole "you can only see them from a spacecraft" argument that gets trotted out constantly.
Anyone been out there and photographed them? I'd love to get out there with a proper camera setup one day.