Improving deceleration of a gas turbine

A gas turbine engine for an aircraft comprises a high-pressure (HP) spool, HP compressor (105, figure 1), first electric machine (117) driven by an HP turbine (107); low-pressure (LP) spool, LP compressor (104), second electric machine (119) driven by an LP turbine (108), and an engine controller (123) configured to, in response to a change of a power lever angle setting indicative of an deceleration event, reduce fuel flow to a combustion system by a fuel metering unit, and operate the first electric machine in a generator mode to reduce the HP spool rotational speed and engine core mass flow. The controller may operate the second electric machine in a generator mode to further reduce engine mass flow. Electrical power may be supplied to an anti-icing system 304, battery 305, or capacitor. A method comprising identifying a condition to the effect that current fuel-air ratio in combustor is indicative of weak extinction onset, and extracting mechanical shaft power from HP spool to prevent further fuel-air ratio drop.