Disappearing aircraft and message "pilot discard chair" when resuming certain saves

[Gorn557]

I have a certain mission where when I save it and resume, about 20 aircraft disappear within a minute with the message in the post-mission log "pilot discard chair", which I have not seen before. Here is the initial and saved mission, and the .trk of the saved mission. 

Saved mission.miz Saved mission track.trk Initial mission.miz

[Gorn557]

I did some looking in Tacview. For some reason, once the save is loaded, a number of the aircraft (look at the B-1Bs, for example) just plummet straight into the ground for no apparent reason. It's not that they were all hit by missiles or something right before the save- it happens to many aircraft, all at once, right after the save is loaded.

Edited April 5 by Gorn557