The McDonnell Douglas F-4X-VG was a design proposal to improve the carrier landing characteristics of the venerable F-4 Phamtom 2 in US Navy service. This eventually lost out to Grumman’s F-14 Tomcat but like the Tomcat the F-4X-VG has a variable geometry wing. The Navy passed on this proposal due to the VG-X’s apparent inablility to carry the AWG-9/AIM-54 Phoenix weapons system suite.
The Lexicans 
Sorry, I’m a bit late to the party.
I’ve actually read quite a bit of praise for the Phantom’s manners behind the boat. Maybe it was colored a bit through Tomcat-tinged hindsight, the landing characteristics of which seemed to earn it no friends, but it surprises me that this was a thing.
I’d guess then it wasn’t so much to improve handling as to improve approach speed, which was on the Tomcat’s to do list. 10 fewer knots on the airplane means 10 more knots’ worth of options for the boat’s skipper, I suppose.