Plane spotters with £2.99 app expose top secret UK spy plane off Russia: Highly-classified mission involving £650m aircraft is watched by thousands online

‘Rivet Joint takes a very sensitive reading of Russian air defences, such as their search radars. It is very useful for the UK and US to know the sorts of patterns that the Russians’ frequency-agile radars operate with. The UK and US aircraft were most likely trying to provoke a response, because usually the Russians wouldn’t broadcast their highest end radar waveforms for Britain and the US to collect and analyse.’