Dobbins the lowest it came down to was 2000ft I believe, first pass after it formed up over Cottersmore over EMA was a lot higher,

Oz plane when they did a formation on the A340 many moons ago, the Pilot said it was a strange site to see the wing time moving up and down about 30 ft in flight, and that in the aircraft you couldn’t see it, which made formating on it interesting …… mind you if they didn’t flex they would fail. 🙂

As an addition, those outrigger wheels on the B-52 are to prevent the wings hitting the ground as they flex on landing