London, Nov. 7 -- A fresh wave of bomb threats disrupted air traffic across Europe on Friday, as flights were diverted, grounded and escorted by fighter jets, in the second major outbreak of false alerts in less than a week.

The affected aircraft landed safely and searches revealed no explosive devices.

The latest alerts affected at least 18 flights to or from Bulgaria, Cyprus, Czechia, France, Hungary, Italy, Portugal, Romania and the UK.

Danish police investigated a threat against Copenhagen airport but the airport's management said it was operating normally. The warnings followed separate threats on Tuesday and Thursday that forced at least 35 flights to be diverted or searched, raising questions over an apparently coordinated effort ...