junkhound...
This is a toughie.
I just happening to be working a lightning issue, though.
From what I can tell, lightning is strictly a cloud-to-ground and cloud-to-cloud phenomena. At/above the -40F level [above +35,000--40,000-ft level] lightning becomes rare. Above cloud-tops, lightning ceases to be a problem.
From the research I've seen, "red-sprites" appear to be similar to corona discharges that emanate from very high altitude [~+50,000-Ft] cloud-tops and radiate into space... kind’a like a reverse Aurora.
To my limited knowledge, aircraft have not seen any affects fro red-sprites for (2) primary reasons:
(1) Extreme altitude. There are only a few acft capable of getting safely between these extremely high cloud tops and space. I believe that turbulence avoidance generally mandates a significant clearance distance for safety... so most acft just avoid flying over these cloud systems.
(2) If an acft is capable of such high altitude flight, it HAS to withstand, and completely dissipate, corona-build-up [static-electric build-up that can spark/arc with extremely high energy]. Therefore, when encountered, a Red Sprite is "no-big-deal" [not noticeable]. NOTE: I think Red Sprites are only visible at a shallow angle from a distance... against an appropriate background… so the crew should be unaware of an encounter!
Regards, Wil Taylor