A pilot flying above Norfolk was among seven aviators who reported close encounters with objects which might have been balloons in UK air space last year.
Decisions by the US authorities to shoot down a series of objects in western airspace in recent days, including a suspected Chinese spy balloon, have heightened tensions.
It prompted prime minister Rishi Sunak to say the government would do "whatever it takes" to keep the UK safe from the threat of spy balloons.
And analysis of UK Airprox Board data by the Press Association has revealed Norfolk features in a tally of possible balloon encounters pilots had in 2022.
On June 3, the pilot of an Airbus A321 aircraft climbing to 35,000ft, about 15 miles east of Norwich, reported "a small white weather balloon with a small box on a short tether" in front of the aircraft.
The balloon disappeared about 300ft to 500ft below the aircraft as they passed 34,000ft.
The pilot reported the sighting and that the risk of collision was "medium", which triggered the Airprox investigation.
The UK Airprox Board said the "reported altitude or description of the object were sufficient to indicate that it was probably a balloon".
The report added: "The board considered that the pilot’s overall account of the incident portrayed a situation where although safety had been reduced, there had been no risk of collision."
Among other reports by UK pilots were of a "balloon or an egg-shaped drone" flying at 1,850 feet above Enfield in London in December.
In September, an Airbus A319 pilot had been "distracted" by an object which was "either a balloon or a drone" passing along the side of the plane.
In October 2017, the Met Office said it "launches over 4,300 balloons every year from six locations across the UK".
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