It would be worth remembering that big-jet formation was a regular occurrence for AAR in the RAF and, could be flown in day/night/IMC, mixed (big-jet!) formation and without briefing, or any of the items listed in KenVs post.
AAR formation flying is VERY different than tactical airdrop formation flying. In large tactical airdrops, there are a large number of aircraft (from a dozen to mulitple dozens of aircraft) that must maintain a tight formation while simultaneously maneuvering at low altitude, both day and night. This is difficult and dangerous to do in the best of circumstances, but especially so at night using NVG. I don't see how it can be done at night with NVGs without electroluminescent formation lights, that's why I'm asking if Airbus has come up with a different solution for the A400M
The same with eyebrow windows. If you are in a formation with another airlifter on either side of yours, when the formation makes a 30 degree bank to the left the aircraft on the left will be obscured by the cockpit ceiling. In these A350 formation flights individual aircraft "peeled off"
one at a time while the rest of the formation continued straight ahead. This resulted in the distance between the turning aircraft ALWAYS increasing during the entire turn. In a tactical formation drop every aircraft MUST maintain relative position to every other aircraft in the formation (in the US this is called "Station Keeping"), even during climbs, descents, and turns. That means the aircraft on the inside of the turn must slow down while the aircraft on the outside of the turn must speed up in order to maintain relative position. This means each pilot
must be able to see the aircaft next to him on the inside of the turn. I don't see how this can be done without eyebrow windows. Or has Airbus come up with another solution? For example, US C-130, C-141, and C-17 aircraft have SKE (Station Keeping Equipment) which does this electronically when formation flying in IMC. But using SKE (generally) requires a looser formation than flying by eye. The eyebrow windows in (most) tactical airlifters are there for a very good reason. It was not arbitrary.
And the knee windows are critical when operating on small austere airfields by allowing the pilots to see downward from the cockpit so they can safely maneuver close to the edges of runways, taxiways, and ramp areas. Has Airbus come up with a different solution? For example, the downward and rearward visibility in an F-35 is restricted relative to other modern fighters. However, Lockheed solved that problem by mounting multiple cameras on the aircraft and sending video to the helmet mounted display. The pilot can thus look "through" the sides, back and even floor of his cockpit. Has Airbus done something along those lines on the A400?