Data off the ADS-B capable transponder of the aircraft suggest the aircraft was descending to enter the hold at about 340 knots over ground on a track of 315 degrees, when descending through FL229 at 17:47L (09:47Z) the speed decayed to 290 knots over ground still on a track of 315 degrees before increasing to above 400 knots over ground in altitude fluctuations between FL214 and FL230 before levelling off at FL220 at 390 knots over ground subsequently reducing to 340 knots over ground.