Accidents can happen, as the song goes. But for the Pentagon, the Russians tempted fate when they first dumped fuel on a US reaper drone and then clipped the unmanned surveillance craft. While the US tries to carefully manage its nuclear-armed rivalry with Moscow, NATO allies harbour no such qualms about showing support for Ukraine. Slovakia is pledging a fleet of 13 MiG-29 Soviet-era warplanes to Ukraine, the second former Warsaw Pact nation in as many days to answer Kyiv's long-running request after Poland pledged four of them.