Yes it is true that SIA's engineers are mostly in SIAEC, but SIAEC is 80% owned by SIA, so under SIA Group accounts, they have 22,000 staff including those in SIAEC, who for all intents and purposes are SIA staff. (Like QF Engineers are probably under a department or entity called Qantas Engineering) So in the Group accounts, they're all consolidated. ST Aero is a competitor to SIAEC, SIA does not use them or their suppliers. From what little I know, the way SIAEC undercut ST Aero and other MROs was they used marginal costing, as all overheads were allocated to SIA. Non-SIA work was taken on as overflow if there were spare resources available, in between SIA work, to take them on. It also annoys ST Aero, because without the legacy airline baggage, ST Aero is a more efficient outfit than SIAEC.