I probably will regret getting into this, but since Bruce has brought this up 'yes' there are differences between the 1988 Schaffner sketch of Cooper prepared by a forensic artist for Unsolved Mysteries vs. the original Mucklow-Schaffner sketch presumably reflecting some consensus between the two women back in 1971-72.
1. the hairlines are different.
2. facial proportions (bone structure) is different.
3. neck and chin fat ('secret clue' turkey neck feature) is more prominent in the 1988 sketch.
4. length of nose and nostrils are different.
5. cheeks are more sunken in the 1988 sketch.
6. Cooper's expression is totally different. Cooper looks more sad, surely, and dangerous - a criminal type.
7. there is more evidence of age and a sullen posture.
17 years has passed between these two sketches. Mucklow's and Schaffner's personalities were different in 1971 and changed differently through the years. If you can believe the Smith ideology, Mucklow became an emotional basket case, unreliable, and a virtual hermit evading the public while we know Schaffner got married and was having a solid social-emotional self-supporting life. *Going back to 1971, we know that Cooper made a critical decision early in the hijacking when he chose the more compliant Mucklow over the far more resistant Schaffner as his primary hostage, workhorse, and fictitiously empathetic go-between, which in reality Tina never was. This decision on Cooper's part was practical and relied on his personal judgement that the last thing he wanted or needed was a sharp-tongued savvy female stewardess to have to have to deal with, namely Ms. Schaffner!
In my opinion, these two sketches reflect different 'emotional memories' of (and reactions to) Cooper taken at different times. The joint sketch done in 71/72 by agreement between Schaffner and Mucklow is probably the more neutral rendering of a 'consensus Cooper'. Flo's 1988 sketch shows a criminal Cooper - someone dark, sullen, aged, and dangerous. What the program should have done (and maybe tried but failed to do) was to have met with Tina to get her 1988 memory of Cooper, 17 years after the fact.
Was Flo's memory better (more accurate) in 1988 than in 1971? I don't know.