Visible are KC-135 tankers and B-52s. The island is a joint military installation shared by British and American forces. B-2 protective hangers can be seen (opposite north facing B-52s).
Use Google Earth historical imagery - time slider 4/12/2006
Planes on Diego Garcia Island
This map has better detail in Google Earth than Google Maps
cheers
I saw them on google map one or two years ago...