A hardly known fact is that United States frequently operate remotely operated drones over Eastern Ukraine to observe Eastern Ukraine and parts of Russia.
So far there are no indications these drones operated around July 2014 when MH17 was shot down.
The Aviationist reported in October 2016 about RQ-4 Global Hawk UASs (Unmanned Aerial Systems) operating over Eastern Ukraine. The Global Hawk provides persistent near-real-time coverage using imagery intelligence (IMINT), signals intelligence (SIGINT) and moving target indicator (MTI) sensors. The RQ-4 has an endurance of more than 34 hours.
RQ-4 operate from very high altitudes far above the upper limit where commercial airlines operate. 50.000 feet (flight level 500) is the operating altitude for the RQ-4 which operates out of Sigonella Naval Air Station in Italy. It has photographic reconnaissance capabilities as well as electronic reconnaissance, meant to find the location, operating conditions and emission characteristics of radar air defense systems. The drone’s developer, Northrop Grumman, has recently been engaged in testing of an RQ-4 with an optical high resolution camera of the kind normally fitted on U-2 aircraft, along with testing of the Syers-2 multispectral electro-optical camera.
Most of the times flights of RQ-4 are not spotted. However sometimes the ADS-B transponder is not switched off and the drone can be spotted at Flightradar 24. Such happened at October 15 2016.
This image shows the route of another RQ-4 over Ukraine at December 2, 2016
Besides drones, the US also operates US P-8A Poseidon ASW patrol aircraft (based on the Boeing 737), also stationed at Sigonella, in the area.