AIRCRAFT pilots have been asked to respect an informal no-fly zone over Edinburgh Zoo following fears that the noise from low-flying planes and helicopters could cause the pregnant panda to lose her cub.

Bosses at the zoo have asked the Civil Aviation Authority to issue a Notice To Airmen, known to pilots as a NOTAM, which are usually used to alert them to unexpected hazards, such as cranes, or changes to communications procedures.

However, it has emerged a notice has been published asking that the airspace above the zoo is avoided if possible to prevent disruption to its animal inhabitants. It is understood it is a particular issue at the moment because of the extra air traffic brought by the festival and the Military Tattoo.

One helicopter operator said they had been led to believe the notices had been put in place during the crucial early stages of the panda's pregnancy.

It is hoped the 10-year-old will give birth at the end of this month, after she was artificially inseminated in April.

A source at Edinburgh Zoo said that while the NOTAM had mainly been set up to protect its breeding penguin colony, the pregnancy of the female giant panda Tian Tian had also been a factor.

A spokeswoman said: "Edinburgh Zoo has a NOTAM in place over its airspace to prevent disturbance to all animals in the collection, yet it is mainly asked in consideration of the breeding penguin colony.

"It is particularly relevant at this time of year due to the regular increased activity of low flying aircraft and hovering helicopters which occur as a result of the festival. We have been in contact with the Military Tattoo and the RAF for several years now and they have both always been very supportive and considerate of our requests."

Last year experts believed Tian Tian became pregnant but lost her cub at late term. Although panda pregnancies are notoriously unpredictable, the latest scientific data suggests she is on course to give birth to the first panda in Scotland.

The NOTAM does not constitute an official no-fly zone, although pilots are expected to respect them in usual circumstances. Other NOTAMS in Scotland in recent days include a warning about a model rocket firing event in Ayrshire, an air display in Strathaven, a fireworks display in Dumfries and kite flying in Girvan.

Police Scotland is among the bodies that was made aware of the notice and took it into account when flying its helicopter in the Edinburgh region. However, the force was prepared to fly over the zoo if necessary in an emergency.