A week of hoax bomb threats and a separate hacking campaign have left European aviation and retail security scrambling, with fighter jets scrambled to escort passenger planes and supermarket refrigeration systems knocked offline in nine countries.

At least 27 passenger flights across Europe were disrupted by hoax bomb threats in a single day last week, forcing several planes into unplanned landings and prompting military jets to intercept or escort others, according to ITV News. Hungary's defense minister said fighter jets escorted three separate passenger planes across the country's airspace within a single hour after each received a bomb threat.

A tiny fraction, a huge disruption

Air traffic regulator Eurocontrol tried to put the chaos in perspective, noting that the 14 flights it was aware of with threats on the worst day represented just 0.05% of the nearly 26,300 flights that crossed the European network that day, per CTV News. Still, no explosives have been found on any targeted aircraft, and authorities have not identified who is responsible. Some officials have pointed to suspected Russian hybrid activity, but investigators say that link remains unproven.

Running alongside the flight hoaxes is a separate and seemingly unconnected cyberattack: hackers knocked out refrigeration systems at supermarkets across nine European countries, with confirmed incidents in the UK and Germany and knock-on effects at French blood banks, according to wire reports. Some stores reported their refrigeration units heating up to roughly 122 degrees Fahrenheit overnight before the problem was caught.

"ONE OF THE MOST ROBUST AVIATION SECURITY SYSTEMS IN THE WORLD"

That's how one airline described Europe's existing defenses in response to the threats, even as transport officials acknowledged the current wave has stretched resources. Security officials from across the bloc are set to meet in Brussels this week to hammer out new measures for handling the surge in hoax threats, a response that underscores how seriously governments are taking even unconfirmed warnings.

For travelers, the practical effect has been a string of delays, diversions and tense hours on tarmacs, even though every threat investigated so far has turned out to be a hoax. For retailers and blood banks, it's been a scramble to protect perishable goods and medical supplies from a vulnerability few had previously planned for.

Investigators in multiple countries are continuing to trace the source of both campaigns, and officials have cautioned that more disruption could follow before anyone is identified or caught.