- Summary- Malfunction not escalation blamed for incident- Wallace says U.S. trip no cause for alarm- But incident highlights risk of miscalculationLONDON, Oct 20 (Reuters) - A Russian fighter jet released a missile near an unarmed British spy plane patrolling in international airspace over the Black Sea on Sept. 29, UK defence minister Ben Wallace said, in an apparent accident and not a deliberate escalation of tensions.Britain has condemned Russia for invading Ukraine and hit Moscow with punitive sanctions while giving military and civil support to Kyiv, and relations between the two countries are at historic lows.He said Russia acknowledged that the incident took place in international airspace, adding that patrols have now resumed, and British aircraft were now being accompanied by fighter aircraft escorts.Wallace repeated that there would be "severe consequences" for Russia if it used nuclear weapons in Ukraine, adding that he discussed Ukraine's battlefield successes and the possible Russian response to them on the trip."We are dealing with a president and indeed a Russian forces who, as we've seen from the Rivet Joint incident, are not beyond making the wrong calculation or indeed deciding that the rules don't apply to them.""