To reiterate what I said on another thread. That “neutral” plane parked on the Phoenix tarmac in summer would have been absolutely sweltering inside.....unless the engines had been left running and the AC going full blast. In which case, the plot becomes a lot thicker.
Per this story, it mentioned several times that the meet was on her plane - there appears to have been no ‘neutral’ 3rd plane. The only time I’ve heard about a 3rd plane was a mention from Rush - frankly, the way some of the earlier stories were written (poorly) it would be easy to get confused.
If there had been a 3rd/neutral plane, or even Lynch’s plane sitting on the tarmac, cabin air & electric power can be run by the APU (auxilliary power unit) without the main engines being started so it would not have been hot inside.