My understanding just based on what I have read (so, at face value) is that since Iran is the only other country who has them, the US wanted no parts to get to them, so part of their decommissioning (inactivation?) was that they could be used in museums or as stationary 'memorials' (props), but would never be made to be airworthy airframes again.
The idea of selling Iran rare F-14 Tomcat parts so it didn't have to cannibalize its own F-14 inventory was preposterous.
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It is now more certain than ever that Mav's old mount will have a central role in the film.
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In the case of the Phantoms, dozens of countries had them and were flying them until recently and you could get parts from a number of vendors, but given that Iran is part of the Axis of Evil and all, they get no leftover F-14 parts.
I love the F-14, and fondly recall when they still flew. I hate that they were retired, but kinda, sorta get the argument why.