Boeing's E-X project

Pic. Source : https://www.secretprojects.co.uk/forum/index.php

 As a candidate of surveillance aircraft of USN, Boeing had proposed joint wing design. Most of the sensors are mounted on the wing, and Boeing insists it could cover and provide better sensor capability than existing systems. 

 It should be noted that complex flow pattern at the wing tip of the joint wing is studied via wind-tunnel testing. Fuselage design is similar to S-3, and engine pod is attached at the side of the body where downstream of the wing is worried. 

 Joint wing is expected to have advantage in lift/drag ratio and structural fatigue aspect, and this is why Boeing chosen this design for long-time endurance aircraft. But, sill, complex control of CG, and engine position could be trouble some phenomena when the design of the aircraft is matured. 

 Additionally, rear wing part tends to be lower or higher position than front wing to avoid downstream of the front wing which degrades performance and handling qualities or stability. In that design, if rear wing is swallowed by downstream of the front wing, aircraft could enter the severe departure status than the conventional ones.