Dear Sir,
I am an exploration geologist with a large field experience. Also in GIS, Remote Sensing and other connected domains.
I was involved in the design for a helicopter flight plan, around 600 km length. The delivered product asked by the pilot (after some tuning discussions with him) was a kml file (for Google Earth). For internal use I made also a KP (kilometer point) markers files, in csv format (x,y,z format according to your demand).
Also, I was involved in the path design for a drone surveys (imagines).
Again, delivered as a kml file, but any time I can generate the x, y, z file at the resolution demanded by your purposes.
All this flight paths I can superpose on satellite imagery products (like Google Earth) or 3D view of the ground (relief, mountains, valleys, etc) basis on high resolution RADAR data (free) or where it is available, free LIDAR data. I consider this useful for your presentations in front of the clients.
Hooping that my skills are useful for your project I remain at your disposals.
Kind regards,
Iulian Seba