British Airways will deploy a Boeing 777 on its Heathrow to Jeddah route next year.
The change, which comes into effect on March 31, will result in an additional 250 seats each week. The route is currently served by a B767.
Passengers will be able to travel in First or Club World.
BA configures its B777 with 14 suites in First, 48 fully flat-bed seats in Club World, 40 seats in World Traveller Plus and 124 seats in the World Traveller economy.
Paolo De Renzis, BA's area commercial manager, Middle East and Central Asia, said: "It is our aim to offer our Saudi travellers the very best in-air experience possible, and our new First cabin brings classic British elegance with attention paid to every detail every step of the way."
To read a review of a BA flight on a B777 from Chengdu to London, click here.