Ah, I think the damage explains it. Seems the gear suspension isn't strong enough. The [contact_points] entries define the gear in Aircraft.cfg. Open a default Aircraft.cfg in Notepad for an explanation. Each problem aircraft would have to be tweaked individually to fix it. It's a tad complicated & could take a little figuring out if you're not used to it.
Maybe use the original default flight at Meigs. Then change aircraft & see if that helps.
PS. My tute here explains the problem.
http://www.simviation.com/lair/Sinking.htmIt will only definitely fix the aircraft used as an example but might give you an idea of where to start.
PPS. Think I found the Frontier Airlines DC-3 in your shot. I used the variable from the CFS2 default C-47 & it seems to work fine. Try changing the entry mentioned in my tute to 0.44 (instead of 0.2). Here's the complete line.
point.0= 1.000, -38.417, 0.000, -0.833, 1574.803, 0.000, 0.666, 57.660,
0.44, 2.500, 0.916, 33.000, 33.000, 0.000, 0.000, 0.000