John Collings proposed to Naomi Lonney in mid-air

They had ordered an independent study to ensure balloonists could not risk spreading foot-and-mouth disease by landing on farmland.

About 30 balloons were due to lift off at 0600 BST on Friday.

Bristol International Balloon Fiesta organisers cancelled their flights, despite "lovely" conditions, because the wind would have taken pilots over farmland.

A spokeswoman said: "In normal years we would have flown. It was a very close call to make."

Human pyramid

The balloons were inflated but remained tethered to the ground by anchor ropes.

Several displayed banners in support of British farmers.

Balloonists fired their burners for a fiesta pop concert

One pilot relaxed in a hammock strung between balloons 40 feet off the ground.

The fiesta began on Thursday with a pop concert featuring Atomic Kitten, Steps and Emma Bunton, among other acts. Thousands attended despite the rain.

Flights are scheduled at 0600 and 1800 BST every day until Sunday evening.

Organisers are optimistic that some will go ahead.

BBC Bristol Online is staging live webcasts from the fiesta.