U-2, as far as I know. I only flew it three times, but holy shit, it's... different. 
 
	 
 
	On the KC it was the combination of low engines, fast approach speeds, and the cable driven ailerons and elevators delaying all the inputs. Then you had a huge hydraulic rudder that would throw the plane around much faster than the cable driven surfaces. It had so much inertia that if you didn't pull the power at the right point, you couldn't slow down. If I remember correctly we went to idle at 200-300 feet for the flaps 30 (engine out) approach when heavy.
 
	 
 
	I also can't compare it to the fighters that were around in your day, because they only keep the planes, not the pilots in the museums 😂🤣. I suspect some of those rocket ships with stubby little wings were an absolute monster to fly, but everything we have now is so much more advanced. 
 
	 
 
	The difference between the U2 and the kc-135 was not close, I don't want to make it sound like the kc-135 was unmanageable. After all, many of the world pilot training students flew it just fine. But when I talked to pilots who had flown both fighter aircraft and the kc-135, the raw stick and rudder of the kc-135 was more to manage. 
 
	 
 
	It was just really sloppy. You made up for it with probably the easiest combat mission in the AF. I taught many many KC135 pilots that were barely able to fly the plane, much less handle a more complicated mission.
 
	 
 
	Honestly the biggest argument I have in support of the kc-135 being harder to land than a fighter is that the fighters weren't doing touch and gos when I was in. That blew my mind. There's no way you could get proficient at flying the kc-135 without doing pattern only flights. But you also have the better pilot factor to deal with, for whatever that equalizes.