ATC for 60,000ft+
Do aircraft such as the U-2S Dragon need to keep in contact with ATC at FL600 and above? Obviously not a lot is going to be in the way re: collision avoidance etc and so the pilot surely can just get on with his routing or mission and re-contact the ATC Agency when he is ready to descend.
Or does the pilot need to keep in regular contact for DnD purposes, whereby if contact is not made for what, 45 mins? then the DnD cell is contacted.