Almost 25 years ago, a large runaway weather balloon proved to be quite challenge a for a pair of fighter jets trying to shoot it down, staying in the air even after more than 1,000 rounds were fired at it.

The research balloon was measuring ozone levels above Canada, the Associated Press reported at the time. It went rogue in August 1998, passing across Canada, over the Atlantic Ocean, and through British airspace before entering Iceland’s airspace and then drifting northward.

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Two Royal Canadian Air Force CF-18 fighter aircraft spotted the balloon over Newfoundland and fired more than 1,000 rounds at it. The AP reported that the jets, Canadian variants of the American F/A-18 Hornet, hit the balloon, but rather than popping or exploding and crashing to the earth, it slowly began leaking helium. The big balloon was still in the air.

Read more: yahoo