Originally Posted by Schind

Over 90% of all Trent engines are on long term service agreements with airlines paying per hour so most of the time they'll get back another engine but they may receive an upgraded engine, or parts of one, they previously had by chance. The Trent XE upgrades are being done in Derby, Germany and Singapore. You'd imagine the BA and Virgin engines will all be overhauled in the UK to save transportation costs so that'll be the pool of engines rotated, alongside new builds. I can't think of other airlines who have RR 787s where logistics make Derby the best place to send them.