https://www.reuters.com/article/us-venezuela-politics-general/venezuelan-general-recognizes-opposition-leader-guaido-as-president-twitter-video-idUSKCN1PR0E1General Francisco Yañez of the Venezuelan Air Force - Director of Strategic Planning of the Military High Command of Aviation - is the first high ranking military officer to reject Maduro and recognize Juan Guaidó as President per a video released today. Among other things, General Yañez claimed Maduro has two planes ready for escaping and that 90% of the Armed Forces were against him (last claim is excessively dubious), and asserted that he would only follow Guaidó's orders as his commander-in-chief.
The Venezuelan Government has predictably branded Yañez a traitor and emphasized that by virtue of his current office he does not command troops (although he does have critical planning responsibilities within the Air Force). It remains unclear whether Yañez is still in Venezuela or may have been forced to flee into Colombia, and the opposition is leading another series of mass protests today.
Senator Rubio, in the meantime, claims there's at least some seven high ranking offers wanting to do the same:
https://twitter.com/marcorubio/status/1091727109100326912