jeena,
Yes, I agree with you. So why not?
Either JR thought this one through and arrived at it being too risky, i.e. caught with a dead JonBenet in his car, had to result in a jail sentence?
Or Patsy vetoed it, she could not bring herself to dump JonBenet out in the cold?
Alternatively, the parent(s) found JonBenet too late to dispose of JonBenet outdoors and accomplish all the staging?
I reckon the latter otherwise what was going on for the best part of 5-hours?
.
Or he and PR were too busy staging the crime and simply forgot to cancel the flight (if my previous answer doesn't suffice).