LONDON — British investigators say a bundle of large party balloons almost caused a collision with a business jet shortly after take-off from London City Airport.

Britain’s airport safety investigators known as Airprox said Saturday that good fortune helped the Oct. 6 incident from turning into a disaster.

The Cessna private jet was climbing toward cruising altitude when one of the pilots spotted about 20 black and yellow balloons and shouted “watch out.”

Officials say the jet’s auto-pilot was disconnected and the crew maneuvered it to miss the large balloons.

It was one of 15 near misses evaluated by the safety board at its monthly meeting.