A bird wiped out in England in the 19th Century could return on Monday - after overcoming a last-minute paperwork hitch.
The bird has not been seen in Britain since 1832
The great bustard is the world's heaviest flying bird and can weigh up to 20kg and stand to the height of an adult roe deer.
A plan to hatch chicks in Russia and release them on Salisbury Plain was due for completion earlier this year.
But complications arose when Russian paperwork delayed their departure.
The chicks are being flown in for release under a joint project between the Salisbury-based Great Bustard Group and the University of Stirling, working with Russian partners.
The birds were eventually granted an export licence when the UK government stepped in.
After an initial check at a UK airport's animal reception centre, they will have to spend a month in quarantine.
They will then be moved to "soft pens", where
they will become accustomed to outdoor conditions while still being safe from predators.
The biggest natural enemy to the bird is the fox, and the bustard group plans to place a stuffed version in the pen to help the birds learn to recognise it.