http://www.au.af.mil/au/awc/awcgate/crs/rl30114.pdf

There is no any proves, that NATO attacks thru Romanian and Bulgarian aerospace...

OK, Macedonia and Romania are out, one more left...

It has a PESA radar, IIRC.

Technically you really shouldn't 'have the chance' of facing B-2's in Serbia. Their ESM systems and mission profile should prevent them from ever flying into a SAM's detection range.

Publication Title Jane's Avionics
Publication date Apr 30, 2009
Section Airborne electronic warfare (EW) systems
TITLE : AN/APR-50 Defensive Management Suite (DMS)

TEXT : TypeAirborne Electronic Counter Measures (ECM), Electronic Support Measures(ESM) and Radar Warning Receiver (RWR) system.DescriptionAN/APR-50 Defensive Management System (DMS) is installed in USAF B-2aircraft. The system is classified and very few technical details havebeen released. It is believed that the system is designed to presentaircrew with intercepted emitter information overlaid on a pre-programmeddisplay of known emitter locations. The installation features a number ofantennas, distributed all around the airframe, feeding nine radiofrequency front ends, which detect and analyse a wide variety of signals.Each of these front ends may be tuned to a different part of the frequencyspectrum. Five receivers take the outputs of the front ends and pass themto the processor.There is considerable speculation that the AN/APR-50 utilises an ECMtechnique known as ’active cancellation’ - this stealth technique employsan array of antennas to transmit a signal which is out of phase withincoming radar emissions, thus effectively reducing the intensity of thereflected returns through interference. If the emitted interferencesignal, travelling in the same direction, is exactly matched in terms ofamplitude, period and phase, to the reflected radar signal, then thethreat radar would not be able to detect any return signal, thus failingto ’see’ the aircraft. This is called destructive interference. In termsof applying such ECM techniques to an airborne platform, incoming signalswill have many different characteristics of amplitude, period and phase,which, combined with the many different directions of reflection,resulting in phase/amplitude shift, will make true ’cancellation’extremely difficult to achieve in the real world. It is more likely thatthe characteristics of the strongest incident signal would be selected bythe system processor for destructive interference.Operational statusThe Northrop Grumman Company designation of the system is ZSR-63. InJanuary 1993, Northrop Grumman was awarded a US$117 million contract tocontinue development of the AN/APR-50. Northrop Grumman was also awardedUS$53.9 million to carry on with ESM development, including extension ofthe frequency range. It is believed that this was originally for Band 2and the extension was to cover Band 4 from 500 MHz to 1 GHz. While it isbelieved that baseline versions of the system failed to meet operationalexpectations, software changes completed during the second quarter of 1998were incorporated to address these problems. AN/APR-50 systems installedin Block 30 aircraft are described as ’fully capable in Bands 1 to 4’.Additional software upgrades were implemented during 2001-2002.

To compound this, the B-2 can drop munitions from a fairly long distance depending on its flight profile. The GBU's it drops are essentially glide-bombs, and they will happily glide for a little while ... so there's a bit more stand-off capability than for the F-117.