PARIS, June 11 (Reuters) - Saudi startup Riyadh Air is

set to place a firm order for 25 Airbus A350-1000 jets,

industry sources said.

The airline, previously reported to be considering buying up

to 50 jets, will finalise the order at next week's Paris

Airshow, where fellow Public Investment Fund subsidiary AviLease

is also seen as close to a deal for 40 Airbus planes.

Both Saudi companies have also placed orders for Boeing ( BA )

jets.

Airbus and Riyadh Air declined to comment.