Originally Posted by
Tourist
Well, follow the upgrade cycle of F15 or Tornado or Harrier etc and it seems fairly standard. The cost is as substantial as the upgrade.
F-15A/B to C/D was mainly just avionics, F-15E was more comprehensive and as such was not really an upgrade. Tornado GR1 to GR.4 was mainly just avionics (F.3 excepted with it's fuselage stretch), the Harrier GR.1 to GR.3 was mainly avionics and a LRMTS added to the front, the FRS.1 was avionics and a new cockpit section, the FRS.1 to FA.2 was mainly avionics, the Harrier II/GR.5/7/9 was a complete redesign and not an upgrade. So using your quoted examples as what constitutes an upgraded airframe, I still think the JAS-39C to E is a little more significant...
You are of course, perfectly entitled to disagree!
-RP