MUNICH (Reuters) -Drone sightings overnight at Germany's Munich airport led to the cancellation and diversion of dozens of flights on the eve of a national holiday, leaving nearly 3,000 passengers stranded and leading politicians to call for a tougher response to drone threats, potentially including shooting them down. The Munich airport disruption was the latest in a series of similar incidents that have rattled European aviation, raising concerns about deniable hybrid attacks on Ukraine's European allies, possibly directed by Russia. The Kremlin has indeed denied any involvement in the incidents.