For a while now Turkey has been barred from having access to the F-35 plane (which is regarded as a very capable military aircraft). Trump has been making noises about allowing Turkey to buy it. This is strongly opposed by Greece and Israel as they are in an emerging block opposed to that Turkey is in, with Saudi Arabia-Pakistan-Turkey-Qatar-Egypt (plus dependents) on one side and UAE-India-Greece-Israel-Ethiopia (plus dependents) on the other. Both Greece and Israel already have the F-35, and it contains Israeli components that Israel would prefer not to have accessible to Turkey.
One potential obstacle is the S-400 system that Turkey bought from Russia after it did not secure the Patriot deal that it wanted. That was the stated reason for Turkey being kicked from the F-35 program so as to not have easy Russian access to information about the F-35 in an air defense context. Options have been floated for Turkey to sell it back to Russia or to a third party; Russia has stated that they’d be happy to buy it back (many will know they are in a crunch for air defenses right now) but the unpalatable aspect of that is that that would shore up Russia in the war against Ukraine, which runs counter to other Turkish efforts to militarily support Ukraine. On the other hand, to sell to a third party if they cannot get Russia to sign off would mean that they get a reputation for playing fast and loose with the contracts for military equipment sold to them, which closes doors to more sensitive technologies that other countries may not want to expose to the whims of politics and more expensive contracts to bake in the cost of that extra risk upfront.
The prospect of selling the F-35 to Turkey has some of both Republicans and Democrats opposed. Republican Mike Lawler and Democrat Dina Titus are spearheading efforts to block the sale of the F-35 citing matters ranging from the S-400 to the Turkish occupation of North Cyprus, increasing anti-Israel rhetoric and more.